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@@ -0,0 +1,58 @@
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+func minStickers(stickers []string, target string) int {
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+ n := len(stickers)
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+ options := make([][26]int, n)
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+ goal := [26]int{}
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+ set1, set2 := cntFreq(target, goal[:]), 0
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+ for i, s := range stickers {
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+ set2 |= cntFreq(s, options[i][:])
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+ }
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+ for mask := 1; mask < 1<<26; mask <<= 1 {
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+ if mask&set1 != 0 && mask&set2 == 0 {
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+ return -1
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+ }
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+ }
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+ dp := make(map[[26]int]int)
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+ return dfs(options, goal, set1, dp)
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+}
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+
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+func dfs(options [][26]int, goal [26]int, set int, dp map[[26]int]int) int {
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+ if v, ok := dp[goal]; ok {
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+ return v
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+ } else if set == 0 {
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+ return 0
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+ }
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+ res := math.MaxInt32
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+ for i := 0; i < len(options); i++ {
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+ ret, next, nset := sub(goal, options[i])
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+ if !ret {
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+ continue
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+ }
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+ if val := dfs(options, next, nset, dp) + 1; val < res {
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+ res = val
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+ }
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+ }
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+ dp[goal] = res
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+ return res
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+}
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+
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+func sub(a, b [26]int) (flag bool, res [26]int, set int) {
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+ for i := 0; i < 26; i++ {
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+ if det := a[i] - b[i]; 0 < det {
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+ res[i] = det
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+ set |= 1 << uint(i)
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+ }
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+ if a[i] != 0 && b[i] != 0 {
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+ flag = true
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+ }
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+ }
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+ return
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+}
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+
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+func cntFreq(word string, freq []int) (set int) {
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+ for _, r := range word {
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+ i := r - 'a'
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+ freq[i]++
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+ set |= 1 << uint(i)
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+ }
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+ return
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+}
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