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438. Find All Anagrams in a String
Medium
Given two strings s and p, return an array of all the start indices of p’s anagrams in s. You may return the answer in any order.
An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
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".
Constraints:
1 <= s.length, p.length <= 3 * 104sandpconsist of lowercase English letters.
Solution
using System;
using System.Collections.Generic;
public class Solution {
public IList<int> FindAnagrams(string s, string p) {
int[] map = new int[26];
for (int index = 0; index < p.Length; ++index) {
map[p[index] - 'a']++;
}
IList<int> res = new List<int>();
int i = 0;
int j = 0;
while (i < s.Length) {
int idx = s[i] - 'a';
// add the new character
map[idx]--;
// if the length is greater than windows length, pop the left charcater in the window
if (i >= p.Length) {
map[s[j++] - 'a']++;
}
bool finish = true;
for (int k = 0; k < 26; k++) {
// if it is not an anagram of string p
if (map[k] != 0) {
finish = false;
break;
}
}
if (i >= p.Length - 1 && finish) {
res.Add(j);
}
i++;
}
return res;
}
}