438. 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".

Rust Solution

struct Solution;

impl Solution {
    fn find_anagrams(s: String, p: String) -> Vec<i32> {
        let mut res: Vec<i32> = vec![];
        let mut ss: Vec<usize> = vec![0; 26];
        let mut sp: Vec<usize> = vec![0; 26];
        let s: Vec<u8> = s.bytes().collect();
        let p: Vec<u8> = p.bytes().collect();
        if s.len() < p.len() {
            return res;
        }
        for i in 0..p.len() {
            let c = s[i] as usize - 'a' as usize;
            ss[c] += 1;
        }
        for i in 0..p.len() {
            let c = p[i] as usize - 'a' as usize;
            sp[c] += 1;
        }
        if ss == sp {
            res.push(0);
        }
        for i in 1..=(s.len() - p.len()) {
            let c = s[i - 1] as usize - 'a' as usize;
            let d = s[..][i + p.len() - 1] as usize - 'a' as usize;
            ss[c] -= 1;
            ss[d] += 1;
            if ss == sp {
                res.push(i as i32);
            }
        }
        res
    }
}

#[test]
fn test() {
    let s = "cbaebabacd".to_string();
    let p = "abc".to_string();
    assert_eq!(Solution::find_anagrams(s, p), vec![0, 6]);
    let s = "abab".to_string();
    let p = "ab".to_string();
    assert_eq!(Solution::find_anagrams(s, p), vec![0, 1, 2]);
}

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