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StringPermutation.java
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StringPermutation.java
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package com.abn.dsalgos.algo.slidingWindo;
import java.util.HashMap;
/*
Given a string and a pattern, find out if the string contains any permutation of the pattern.
*/
public class StringPermutation {
public boolean isStringPermutation(String str, String pattern) {
HashMap<Character, Integer> patternMap = new HashMap<>();
int start = 0;
int count = 0;
int len;
int patternLen = pattern.length();
for (int i = 0; i < patternLen; i++) {
char ch = pattern.charAt(i);
patternMap.put(ch, patternMap.getOrDefault(ch, 0) + 1);
}
for (int i = 0; i < str.length(); i++) {
char ch = str.charAt(i);
if (patternMap.containsKey(ch)) {
patternMap.put(ch, patternMap.get(ch) - 1);
if (patternMap.get(ch) == 0) {
count++;
}
}
if (count == patternMap.size()) {
return true;
}
len = i - start + 1;
if (len >= pattern.length()) {
char startChar = str.charAt(start);
if (patternMap.containsKey(startChar)) {
if (patternMap.get(startChar) == 0) {
count--;
}
patternMap.put(startChar, patternMap.get(startChar) + 1);
}
start++;
}
}
return false;
}
}