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Leetcode438-findAllAnagramsInAString

Posted on Edited on In Views: Valine:
Solution Report of LeetCode Acceptted

Description

Given a string s and a non-empty string p, find all the start indices of p’s anagrams in s.

Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100.

The order of output does not matter.

Example

Example 1:

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Input:
s: "cbaebabacd" p: "abc"

Output:
[0, 6]

Explanation:
The substring with start index = 0 is "cba", which is an anagram of "abc".
The substring with start index = 6 is "bac", which is an anagram of "abc".

Example 2:
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Input:
s: "abab" p: "ab"

Output:
[0, 1, 2]

Explanation:
The substring with start index = 0 is "ab", which is an anagram of "ab".
The substring with start index = 1 is "ba", which is an anagram of "ab".
The substring with start index = 2 is "ab", which is an anagram of "ab".

Solution

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public class Solution {
    public List<Integer> findAnagrams(String s, String p) {
        List<Integer> res = new ArrayList<>();
        if (s == null || s.length() == 0 || p == null || p.length() == 0) return res;
    
        int[] hash = new int[256];
    
        for (char c : p.toCharArray()) {
            hash[c]++;
        }

        int left = 0, right = 0, count = p.length();
    
        while(right < s.length()){
            if (hash[s.charAt(right)] >= 1) count --;
            hash[s.charAt(right)] --;
            right ++;
            
            if (count == 0) res.add(left);
            
            if (right - left == p.length()){
                if (hash[s.charAt(left)] >= 0) count++;
                hash[s.charAt(left)]++;
                left ++;
            }
        }
        return res;
    }
}