LeetCode 727. Minimum Window Subsequence

Problem Statement

impl Solution {
    pub fn min_window(s: String, t: String) -> String {
        let (m, n, mut start, mut min_len) = (s.len(), t.len(), -1, std::i32::MAX);
        let mut dp : Vec<Vec<i32>> = vec![vec![-1; n + 1]; m + 1];
        for i in 0..m + 1 {
            dp[i][0] = i as i32;
        }
        for i in 1..m + 1 {
            for j in 1..std::cmp::min(i, n) + 1 {
                if s.chars().nth(i - 1).unwrap() == t.chars().nth(j - 1).unwrap() {
                    dp[i][j] = dp[i - 1][j - 1];
                } else {
                    dp[i][j] = dp[i - 1][j];
                }
            }

            if dp[i][n] != -1 {
                let len = i - dp[i][n] as usize;
                if min_len as usize > len {
                    min_len = len as i32;
                    start = dp[i][n];
                }
            }
        }

        if start != -1 {
            let slice = &s[start as usize..(start + min_len) as usize];
            return (slice.to_string().clone()).parse().unwrap();
        } else {
            return "".to_string();
        }
    }
}