Solution.rs

use std::collections::{HashSet, VecDeque};

impl Solution {
    pub fn min_stickers(stickers: Vec<String>, target: String) -> i32 {
        let mut q = VecDeque::new();
        q.push_back(0);
        let mut ans = 0;
        let n = target.len();
        let mut vis = HashSet::new();
        vis.insert(0);
        while !q.is_empty() {
            for _ in 0..q.len() {
                let state = q.pop_front().unwrap();
                if state == (1 << n) - 1 {
                    return ans;
                }
                for s in &stickers {
                    let mut nxt = state;
                    let mut cnt = [0; 26];
                    for &c in s.as_bytes() {
                        cnt[(c - b'a') as usize] += 1;
                    }
                    for (i, &c) in target.as_bytes().iter().enumerate() {
                        let idx = (c - b'a') as usize;
                        if (nxt & (1 << i)) == 0 && cnt[idx] > 0 {
                            nxt |= 1 << i;
                            cnt[idx] -= 1;
                        }
                    }
                    if !vis.contains(&nxt) {
                        q.push_back(nxt);
                        vis.insert(nxt);
                    }
                }
            }
            ans += 1;
        }
        -1
    }
}