438. 匹配字符串(顺序不同但个数相同的字符串) Find All Anagrams in a String

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 1:

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:

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".

public class Solution {
	public List<int> FindAnagrams(string s, string p) {
        List<int> list = new List<int>();
        if (string.IsNullOrWhiteSpace(s) || s.Length < p.Length)
            return list;
        int sum = 0;
        int[] pArray = new int[26];
        foreach (char c in p){
            sum = sum + (c - 'a');
            ++pArray[c - 'a'];
        }
        int sum1 = 0;
        int startIndex = 0;
        for (int endIndex = 0; endIndex < s.Length; endIndex++){
            if (pArray[s[endIndex] - 'a'] == 0){
                sum1 = 0;
                startIndex = endIndex + 1;
                continue;
            }
            sum1 += s[endIndex] - 'a';
            if (endIndex - startIndex + 1 == p.Length){
                if(sum1 == sum) list.Add(startIndex);
                sum1 -= s[startIndex++] - 'a';
            }
        }
        return list;
	}
}

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