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| class Solution {
String[] stickers;
String target;
int[] cache;
int m;
public int minStickers(String[] stickers, String target) {
m = target.length();
cache = new int[1 << m];
Arrays.fill(cache, -1);
cache[0] = 0;
this.stickers = stickers;
this.target = target;
int ans = dfs((1 << m) - 1);
return ans <= m ? ans : -1;
}
private int dfs(int mask) {
if (cache[mask] < 0) {
int ans = m + 1;
for (String sticker : stickers) {
int left = mask;
int[] cnt = new int[26];
for (int i = 0; i < sticker.length(); ++i) {
++cnt[sticker.charAt(i) - 'a'];
}
for (int i = 0; i < m; ++i) {
char c = target.charAt(i);
if (((mask >> i) & 1) == 1 && cnt[c - 'a'] > 0) {
cnt[c - 'a']--;
left ^= 1 << i;
}
}
if (left < mask) {
ans = Math.min(ans, dfs(left) + 1);
}
}
cache[mask] = ans;
}
return cache[mask];
}
}
|
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