PermutationInString.java

class Solution {
 public boolean checkInclusion(String s1, String s2) {
 if(s1.length() > s2.length()){
 return false;
 }
 int[] freq = new int[26];
 for(int i = 0; i < s1.length(); i++){
 freq[s1.charAt(i) - 'a']++;
 }
 for(int i = 0; i < s2.length(); i++){
 freq[s2.charAt(i) - 'a']--;
 if(i - s1.length() >= 0){
 freq[s2.charAt(i - s1.length()) - 'a']++;
 }
 if(allZeros(freq)){
 return true;
 }
 }
 return false;
 }
 private boolean allZeros(int[] f){
 for(int i = 0; i < 26; i++){
 if(f[i] != 0){
 return false;
 }
 }
 return true;
 }
}