Leetcode 438. Find All Anagrams in a String (Easy) (cpp)
Tag: Hash Table
Difficulty: Easy
/*
438. Find All Anagrams in a String (Easy)
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".
*/
class Solution {
public:
vector<int> findAnagrams(string s, string p) {
if (s.length() < p.length()) {
return{};
}
vector<int> res;
int mapping[26] = { 0 };
for (char cha : p) {
mapping[cha - 'a']++;
}
int cnt = p.size(), i = 0, j = 0;
while (j < s.length()) {
if (j - i == p.length() && mapping[s[i++] - 'a']++ >= 0) {
cnt++;
}
if (--mapping[s[j++] - 'a'] >= 0) {
cnt--;
}
if (cnt == 0) {
res.push_back(i);
}
}
return res;
}
};