Create 05. Stickers to Spell Word.py

02_Dynamic-Programming/05. Stickers to Spell Word.py

@@ -0,0 +1,42 @@
+# https://leetcode.com/problems/stickers-to-spell-word/
+# https://youtu.be/hsomLb6mUdI
+
+class Solution:
+    def minStickers(self, stickers: List[str], target: str) -> int:
+        targetSet = set(target)
+        stickCount = []
+        for s in stickers:
+            stick = {}
+            for i in s:
+                if i in targetSet:
+                    stick[i] = stick.get(i, 0) + 1
+            stickCount.append(stick)
+
+        dp = {}
+        def dfs(t, stick):
+            if t in dp:
+                return dp[t]
+            res = 1 if stick else 0
+            remainT = ""
+            for c in t:
+                if c in stick and stick[c] > 0:
+                    stick[c] -= 1
+                else:
+                    remainT += c
+
+            if remainT:
+                used = 2**31
+                for stick in stickCount:
+                    if remainT[0] not in stick:
+                        continue
+                    used = min(used, dfs(remainT, stick.copy()))
+                dp[remainT] = used
+                res += used
+            return res
+
+        res = dfs(target, {})
+        return res if res != 2**31 else -1
+
+
+
+# Time: O(2^n)