Develop Reference

Java How to print -1 if the given letter1 is not present

I would like to write a program that is taking letter position from two strings, string1 and string2, then it will check where in string2 we have the same letters used but also print number of indexes and if there is no letter that is in the first string just print -1 . For example I have first string = "reds" second one = "Hello world!", then my output should be:
r: 8, e: 1, d: 10, s: -1
Here is my code:
public static void main(String[] args){
String set1 = "reds";
String set2 = "Hello world!";
for(int i = 0; i < set1.length(); i++)
{
for(int j = 0; j < set2.length();j++)
{
char currentChar = set1.charAt(i);
char currentChar2 = set2.charAt(j);
if(currentChar == currentChar2)
{
System.out.println(currentChar+": "+j);
}
}
}
}
}

Another ways using String.indexOf
Classic for loop
String set1 = "reds";
String set2 = "Hello world!";
for(int i = 0; i < set1.length(); i++){
System.out.println(set1.charAt(i) + " : " + set2.indexOf(set1.charAt(i)));
}
or streams
set1.chars()
.mapToObj(c -> (char)c + " : " + set2.indexOf(c))
.forEach(System.out::println);
Note: if the chars apear more than once in the second string the first index of the chars is printed (use lastIndexOf if you want the last index)

public static void main(String[] args){
String set1 = "reds";
String set2 = "Hello world!";
for(int i = 0; i < set1.length(); i++) {
char currentChar = set1.charAt(i);
boolean found = false;
for(int j = 0; j < set2.length();j++) {
char currentChar2 = set2.charAt(j);
if(currentChar == currentChar2) {
System.out.println(currentChar+": "+j);
found = true;
}
}
if(!found) {
System.out.println(currentChar + ": -1");
}
}
}

It will print every position of the set1 characters into set2.
O(n + m) time complexity, where n and m are the sizes of set1 and set2
O(256) space complexity because of ASCII numbers
public static void main(String[] args){
String set1 = "reds";
String set2 = "Hello world!";
Map<Integer, List<Integer>> map = new HashMap<>(); // key = ascii value of the char, value = list of indexes
for(int i = 0; i < set2.length(); i++){
int key = set2.charAt(i);
if(!map.containsKey(key)){
map.put(key, new ArrayList<>());
}
List<Integer> indexesList = map.get(key);
indexesList.add(i);
map.put(key, indexesList);
}
for(int i = 0; i < set1.length(); i++){
int key = set1.charAt(i);
System.out.print(set1.charAt(i) + ": ");
if(!map.containsKey(key)){
System.out.println(-1);
}
else {
map.get(key).forEach(x-> System.out.print(x+ " "));
System.out.println(); // just for new line
}
}
}

Maximum repeated String in an array

The problem is
how to get the maximum repeated String in an array using only operations on the arrays in java?
so i got into this question in a test and couldn't figure it out.
lets suppose we have an array of string.
str1[] = { "abbey", "bob", "caley", "caley", "zeeman", "abbey", "bob", "abbey" }
str2[] = { "abbey", "bob", "caley", "caley", "zeeman", "abbey", "bob", "abbey", "caley" }
in str1 abbey was maximum repeated, so abbey should be returned and
in str2 abbey and caley both have same number of repetitions and hence we take maximum alphabet as the winner and is returned(caley here).
c > a
so i tried till
import java.util.*;
public class test {
static String highestRepeated(String[] str) {
int n = str.length, num = 0;
String temp;
String str2[] = new String[n / 2];
for (int k = 0;k < n; k++) { // outer comparision
for (int l = k + 1; l < n; l++) { // inner comparision
if (str[k].equals(str[l])) {
// if matched, increase count
num++;
}
}
// I'm stuck here
}
return result;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("enter how many votes");
int n = sc.nextInt();
String[] str = new String[n];
for (int i = 0; i < n; i++) {
Str[i] = sc.nextLine();
}
String res = highestRepeated(str);
System.out.println(res + " is the winner");
}
}
so, how should i take the count of occurrence of each string with and attach it with the string itself.
All this, without using a map and any hashing but just by using arrays?

Here is a (unpolished) solution:
static String highestRepeated(String[] str) {
String[] sorted = Arrays.copyOf(str, str.length);
Arrays.sort(sorted, 0, sorted.length, Comparator.reverseOrder());
String currentString = sorted[0];
String bestString = sorted[0];
int maxCount = 1;
int currentCount = 1;
for (int i = 1 ; i < sorted.length ; i++) {
if (currentString.equals(sorted[i])) {
currentCount++;
} else {
if (maxCount < currentCount) {
maxCount = currentCount;
bestString = currentString;
}
currentString = sorted[i];
currentCount = 1;
}
}
if (currentCount > maxCount) {
return currentString;
}
return bestString;
}
Explanation:
Sort the array from highest to lowest lexicographically. That's what Arrays.sort(sorted, 0, sorted.length, Comparator.reverseOrder()); does. we sort in this order because you want the largest string if there are multiple strings with the same number of repeats.
Now we can just count the strings by looping through the array. We don't need a hash map or anything because we know that there will be no more of a string in the rest of the array when we encounter a different string.
currentString is the string that we are currently counting the number of repeats of, using currentCount. maxCount is the number of occurrence of the most repeated string - bestString - that we have currently counted.
The if statement is pretty self-explanatory: if it is the same string, count it, otherwise see if the previous string we counted (currentCount) appears more times than the current max.
At the end, I check if the last string being counted is more than max. If the last string in the array happens to be the most repeated one, bestString won't be assigned to it because bestString is only assigned when a different string is encountered.
Note that this algorithm does not handle edge cases like empty arrays or only one element arrays. I'm sure you will figure that out yourself.

another version
static String lastMostFrequent(String ... strs) {
if (strs.length == 0) return null;
Arrays.sort(strs);
String str = strs[0];
for (int longest=0, l=1, i=1; i<strs.length; i++) {
if (!strs[i-1].equals(strs[i])) { l=1; continue; }
if (++l < longest) continue;
longest = l;
str = strs[i];
}
return str;
}
change in
if (++l <= longest) continue;
for firstMostFrequent

you can't use == to check if two strings are the same.
try using this instead:
if (str[k].equals(str[l])) {
// if matched, increase count
num++;
}

Look for duplicate values in a String[] without using Sets, Lists, ArrayLists?

Lets say we have this array: String[] arr1 = {"a", "b", "c", "a"};
What I'm trying to do is remove duplicate String (In this case "a") and add its value to another String[] called duplicates. When the duplicate is added to the "duplicates" array, the amount of times it occured wrongfully in the array arr1 is concatenated next to it. (recurredValue + amount) so in this example it would be a 1. I have searched for this before and all of them included usage of Lists, ArrayLists, or Sets. Please do not use any of them.

Use below code:-
public static String[] removeDuplicates(String[] numbersWithDuplicates) {
// Sorting array to bring duplicates together
Arrays.sort(numbersWithDuplicates);
String[] result = new String[numbersWithDuplicates.length];
String[] duplicate = new String[numbersWithDuplicates.length];
String previous = numbersWithDuplicates[0];
result[0] = previous;
int counter=1;
int duplicateCounter=0;
for (int i = 1; i < numbersWithDuplicates.length; i++) {
String ch = numbersWithDuplicates[i];
if (previous != ch) {
result[counter++] = ch;
}
else
{
duplicate[duplicateCounter++]=ch;
}
previous = ch;
}
for (int i = 0; i < result.length; i++) {
System.out.println(result[i]);
}
System.out.println("Duplicate Values are ---");
for (int i = 0; i < duplicate.length; i++) {
System.out.println(duplicate[i]);
}
return result;
}

maybe something like this you can use
public static void main(String[] args) {
String[] arr1 = {"a", "b", "c", "a", "a"};
String[] duplicates = new String[arr1.length];
boolean d = false;
int count = 0;
String dup = "";
for(int i = 0;i < arr1.length;i++){
count = 0;
dup = "";
d = false;
for(int j = 0;j < arr1.length;j++){
if(i != j){
if(arr1[i].equals(arr1[j]) && !arr1[i].equals("")){
arr1[j] = "";
d = true;
count++;
dup = arr1[i];
}
}
}
if(d){
duplicates[i] = dup + count;
d = false;}
}
for(int k = 0;k < duplicates.length;k++)
System.out.println(duplicates[k]);
}

Well, one solution is to create 2 arrays and have one hold the unique strings and the other its integer counter. As you index through your sample string array, add the unique strings and increment the incidents. This is not a very elegant or efficient solution but it should work.

Counting words from array in a string

I have an array of string say
A=["hello", "you"]
I have a string, say
s="hello, hello you are so wonderful"
I need to count the number of occurrence of strings from A in s.
In this case, the number of occurrences is 3 (2 "hello", 1 "you").
How to do this effectively? (A might contains lots of words, and s might be long in practice)

Try:
Map<String, Integer> wordCount = new HashMap<>();
for(String a : dictionnary) {
wordCount.put(a, 0);
}
for(String s : text.split("\\s+")) {
Integer count = wordCount.get(s);
if(count != null) {
wordCount.put(s, count + 1);
}
}

public void countMatches() {
String[] A = {"hello", "you"};
String s = "hello, hello you are so wonderful";
String patternString = "(" + StringUtils.join(A, "|") + ")";
Pattern pattern = Pattern.compile(patternString);
Matcher matcher = pattern.matcher(s);
int count = 0;
while (matcher.find()) {
count++;
}
System.out.println(count);
}
Note that StringUtils is from apache commons. If you don't want to include and additional jar you can just construct that string using a for loop.

HashSet<String> searchWords = new HashSet<String>();
for(String a : dictionary) {
searchWords.add(a);
}
int count = 0;
for(String s : input.split("[ ,]")) {
if(searchWords.contains(s)) {
count++;
}
}

int count =0;
for(int i=0;i<A.length;i++)
{
count = count + s.split(A[i],-1).length - 1;
}
Working Ideone : http://ideone.com/Z9K3JX

This is fully working method with output :)
public static void main(String[] args) {
String[] A={"hello", "you"};
String s= "hello, hello you are so wonderful";
int[] count = new int[A.length];
for (int i = 0; i < A.length; i++) {
count[i] = (s.length() - s.replaceAll(A[i], "").length())/A[i].length();
}
for (int i = 0; i < count.length; i++) {
System.out.println(A[i] + ": " + count[i]);
}
}
What does this line do?
count[i] = (s.length() - s.replaceAll(A[i], "").length())/A[i].length();
This part s.replaceAll(A[i], "") changes all "hello" to empty "" string in the text.
So I take the length of everything s.length() I substract from it the length of same string without that word s.replaceAll(A[i], "").length() and I divide it by the length of that word /A[i].length()
Sample output for this example :
hello: 2
you: 1

You can use the String Tokenizer
Do something like this:
A = ["hello", "you"];
s = "hello, hello you are so wonderful";
StringTokenizer st = new StringTokenizer(s);
while (st.hasMoreElements()) {
for (String i: A) {
if(st.nextToken() == i){
//You can keep going from here
}
}
}

This is what I came up with:
It doesn't create any new objects. It uses String.indexOf(String, int), keeps track of the current index, and increments the occurance-count.
public class SearchWordCount {
public static final void main(String[] ignored) {
String[] searchWords = {"hello", "you"};
String input = "hello, hello you are so wonderful";
for(int i = 0; i < searchWords.length; i++) {
String searchWord = searchWords[i];
System.out.print(searchWord + ": ");
int foundCount = 0;
int currIdx = 0;
while(currIdx != -1) {
currIdx = input.indexOf(searchWord, currIdx);
if(currIdx != -1) {
foundCount++;
currIdx += searchWord.length();
} else {
currIdx = -1;
}
}
System.out.println(foundCount);
}
}
}
Output:
hello: 2
you: 1

Indexes of all occurrences of character in a string

The following code will print 2
String word = "bannanas";
String guess = "n";
int index;
System.out.println(
index = word.indexOf(guess)
);
I would like to know how to get all the indexes of "n" ("guess") in the string "bannanas"
The expected result would be: [2,3,5]

This should print the list of positions without the -1 at the end that Peter Lawrey's solution has had.
int index = word.indexOf(guess);
while (index >= 0) {
System.out.println(index);
index = word.indexOf(guess, index + 1);
}
It can also be done as a for loop:
for (int index = word.indexOf(guess);
index >= 0;
index = word.indexOf(guess, index + 1))
{
System.out.println(index);
}
[Note: if guess can be longer than a single character, then it is possible, by analyzing the guess string, to loop through word faster than the above loops do. The benchmark for such an approach is the Boyer-Moore algorithm. However, the conditions that would favor using such an approach do not seem to be present.]

Try the following (Which does not print -1 at the end now!)
int index = word.indexOf(guess);
while(index >= 0) {
System.out.println(index);
index = word.indexOf(guess, index+1);
}

This can be done in a functional way with Java 9 using regular expression:
Pattern.compile(Pattern.quote(guess)) // sanitize input and create pattern
.matcher(word) // create matcher
.results() // get the MatchResults, Java 9 method
.map(MatchResult::start) // get the first index
.collect(Collectors.toList()) // collect found indices into a list
);
Here's the Kotlin Solution to add this logic as a new a new methods into CharSequence API using extension method:
// Extension method
fun CharSequence.indicesOf(input: String): List<Int> =
Regex(Pattern.quote(input)) // build regex
.findAll(this) // get the matches
.map { it.range.first } // get the index
.toCollection(mutableListOf()) // collect the result as list
// call the methods as
"Banana".indicesOf("a") // [1, 3, 5]

String string = "bannanas";
ArrayList<Integer> list = new ArrayList<Integer>();
char character = 'n';
for(int i = 0; i < string.length(); i++){
if(string.charAt(i) == character){
list.add(i);
}
}
Result would be used like this :
for(Integer i : list){
System.out.println(i);
}
Or as a array :
list.toArray();

With Java9, one can make use of the iterate(int seed, IntPredicate hasNext,IntUnaryOperator next) as follows:-
List<Integer> indexes = IntStream
.iterate(word.indexOf(c), index -> index >= 0, index -> word.indexOf(c, index + 1))
.boxed()
.collect(Collectors.toList());
System.out.printlnt(indexes);

int index = -1;
while((index = text.indexOf("on", index + 1)) >= 0) {
LOG.d("index=" + index);
}

Java 8+
To find all the indexes of a particular character in a String, one can create an IntStream of all the indexes and filter over it.
import java.util.stream.Collectors;
import java.util.stream.IntStream;
//...
String word = "bannanas";
char search = 'n';
//To get List of indexes:
List<Integer> indexes = IntStream.range(0, word.length())
.filter(i -> word.charAt(i) == search).boxed()
.collect(Collectors.toList());
//To get array of indexes:
int[] indexes = IntStream.range(0, word.length())
.filter(i -> word.charAt(i) == search).toArray();

String word = "bannanas";
String guess = "n";
String temp = word;
while(temp.indexOf(guess) != -1) {
int index = temp.indexOf(guess);
System.out.println(index);
temp = temp.substring(index + 1);
}

String input = "GATATATGCG";
String substring = "G";
String temp = input;
String indexOF ="";
int tempIntex=1;
while(temp.indexOf(substring) != -1)
{
int index = temp.indexOf(substring);
indexOF +=(index+tempIntex)+" ";
tempIntex+=(index+1);
temp = temp.substring(index + 1);
}
Log.e("indexOf ","" + indexOF);

Also, if u want to find all indexes of a String in a String.
int index = word.indexOf(guess);
while (index >= 0) {
System.out.println(index);
index = word.indexOf(guess, index + guess.length());
}

I had this problem as well, until I came up with this method.
public static int[] indexesOf(String s, String flag) {
int flagLen = flag.length();
String current = s;
int[] res = new int[s.length()];
int count = 0;
int base = 0;
while(current.contains(flag)) {
int index = current.indexOf(flag);
res[count] = index + base;
base += index + flagLen;
current = current.substring(current.indexOf(flag) + flagLen, current.length());
++ count;
}
return Arrays.copyOf(res, count);
}
This method can be used to find indexes of any flag of any length in a string, for example:
public class Main {
public static void main(String[] args) {
int[] indexes = indexesOf("Hello, yellow jello", "ll");
// Prints [2, 9, 16]
System.out.println(Arrays.toString(indexes));
}
public static int[] indexesOf(String s, String flag) {
int flagLen = flag.length();
String current = s;
int[] res = new int[s.length()];
int count = 0;
int base = 0;
while(current.contains(flag)) {
int index = current.indexOf(flag);
res[count] = index + base;
base += index + flagLen;
current = current.substring(current.indexOf(flag) + flagLen, current.length());
++ count;
}
return Arrays.copyOf(res, count);
}
}

A class for splitting strings I came up with. A short test is provided at the end.
SplitStringUtils.smartSplitToShorterStrings(String str, int maxLen, int maxParts) will split by spaces without breaking words, if possible, and if not, will split by indexes according to maxLen.
Other methods provided to control how it is split: bruteSplitLimit(String str, int maxLen, int maxParts), spaceSplit(String str, int maxLen, int maxParts).
public class SplitStringUtils {
public static String[] smartSplitToShorterStrings(String str, int maxLen, int maxParts) {
if (str.length() <= maxLen) {
return new String[] {str};
}
if (str.length() > maxLen*maxParts) {
return bruteSplitLimit(str, maxLen, maxParts);
}
String[] res = spaceSplit(str, maxLen, maxParts);
if (res != null) {
return res;
}
return bruteSplitLimit(str, maxLen, maxParts);
}
public static String[] bruteSplitLimit(String str, int maxLen, int maxParts) {
String[] bruteArr = bruteSplit(str, maxLen);
String[] ret = Arrays.stream(bruteArr)
.limit(maxParts)
.collect(Collectors.toList())
.toArray(new String[maxParts]);
return ret;
}
public static String[] bruteSplit(String name, int maxLen) {
List<String> res = new ArrayList<>();
int start =0;
int end = maxLen;
while (end <= name.length()) {
String substr = name.substring(start, end);
res.add(substr);
start = end;
end +=maxLen;
}
String substr = name.substring(start, name.length());
res.add(substr);
return res.toArray(new String[res.size()]);
}
public static String[] spaceSplit(String str, int maxLen, int maxParts) {
List<Integer> spaceIndexes = findSplitPoints(str, ' ');
List<Integer> goodSplitIndexes = new ArrayList<>();
int goodIndex = -1;
int curPartMax = maxLen;
for (int i=0; i< spaceIndexes.size(); i++) {
int idx = spaceIndexes.get(i);
if (idx < curPartMax) {
goodIndex = idx;
} else {
goodSplitIndexes.add(goodIndex+1);
curPartMax = goodIndex+1+maxLen;
}
}
if (goodSplitIndexes.get(goodSplitIndexes.size()-1) != str.length()) {
goodSplitIndexes.add(str.length());
}
if (goodSplitIndexes.size()<=maxParts) {
List<String> res = new ArrayList<>();
int start = 0;
for (int i=0; i<goodSplitIndexes.size(); i++) {
int end = goodSplitIndexes.get(i);
if (end-start > maxLen) {
return null;
}
res.add(str.substring(start, end));
start = end;
}
return res.toArray(new String[res.size()]);
}
return null;
}
private static List<Integer> findSplitPoints(String str, char c) {
List<Integer> list = new ArrayList<Integer>();
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) == c) {
list.add(i);
}
}
list.add(str.length());
return list;
}
}
Simple test code:
public static void main(String[] args) {
String [] testStrings = {
"123",
"123 123 123 1123 123 123 123 123 123 123",
"123 54123 5123 513 54w567 3567 e56 73w45 63 567356 735687 4678 4678 u4678 u4678 56rt64w5 6546345",
"1345678934576235784620957029356723578946",
"12764444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444",
"3463356 35673567567 3567 35 3567 35 675 653 673567 777777777777777777777777777777777777777777777777777777777777777777"
};
int max = 35;
int maxparts = 2;
for (String str : testStrings) {
System.out.println("TEST\n |"+str+"|");
printSplitDetails(max, maxparts);
String[] res = smartSplitToShorterStrings(str, max, maxparts);
for (int i=0; i< res.length;i++) {
System.out.println(" "+i+": "+res[i]);
}
System.out.println("===========================================================================================================================================================");
}
}
static void printSplitDetails(int max, int maxparts) {
System.out.print(" X: ");
for (int i=0; i<max*maxparts; i++) {
if (i%max == 0) {
System.out.print("|");
} else {
System.out.print("-");
}
}
System.out.println();
}

This is a java 8 solution.
public int[] solution (String s, String subString){
int initialIndex = s.indexOf(subString);
List<Integer> indexList = new ArrayList<>();
while (initialIndex >=0){
indexList.add(initialIndex);
initialIndex = s.indexOf(subString, initialIndex+1);
}
int [] intA = indexList.stream().mapToInt(i->i).toArray();
return intA;
}

This can be done by iterating myString and shifting fromIndex parameter in indexOf():
int currentIndex = 0;
while (
myString.indexOf(
mySubstring,
currentIndex) >= 0) {
System.out.println(currentIndex);
currentIndex++;
}

Try this
String str = "helloslkhellodjladfjhello";
String findStr = "hello";
System.out.println(StringUtils.countMatches(str, findStr));