PermutationStrings.java

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;

public class PermutationStrings {

    public boolean isPermutation(String s1, String s2){
        if(s1.length()!=s2.length()){
            return false;
        }
        HashMap<Character, Integer> ht = new HashMap<>();
        for(int i=0;i<s1.length();i++){
            char c = s1.charAt(i);
            if(ht.containsKey(c)){
                int val = ht.get(c) + 1;
                ht.put(c, val);
            }else{
                ht.put(c, 1);
            }
        }
        for(int i=0;i<s2.length();i++){
            char c = s2.charAt(i);
            if(ht.containsKey(c)){
                int val = (int)ht.get(c);
                if(val==0){
                    return false;
                }
                val--;
                ht.put(c, val);
            }else{
                return false;
            }
        }
        Set keys = ht.keySet();
        Iterator<Character> iterator = keys.iterator();
        while(iterator.hasNext()){
            char c = iterator.next();
            if(ht.get(c)!=0){
                return false;
            }
        }
        return true;
    }
    public static void main(String args[]){
        String s1 = "sumit";
        String s2 = "mtisu";
        PermutationStrings p = new PermutationStrings();
        System.out.println(s1 +" and "+ s2 + " are permutation of each other? " + p.isPermutation(s1, s2));
        s1 = "xyzab";
        s2 = "bayzxx";
        System.out.println(s1 +" and "+ s2 + " are permutation of each other? " + p.isPermutation(s1, s2));
    }

}