(Leetcode) 438. Find All Anagrams in a String
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:
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".Example2:
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".Code:
public List<Integer> findAnagrams(String s, String p) {
List<Integer> list = new ArrayList<>();
int[] hash = new int[256];
if (s == null || s.length() == 0 || p == null || p.length() == 0) return list;
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--;
if (count == 0) list.add(left);
if (right - left == p.length() && hash[s.charAt(left++)]++ >= 0) count++;
}
return list;
}