leetcode: finished #473

content/leetcode/2023/9.md

@@ -3,6 +3,50 @@ title: 2023.9
 draft: false
 ---
 
+# 2023.9.15
+
+```python
+#
+# @lc app=leetcode.cn id=473 lang=python3
+#
+# [473] 火柴拼正方形
+#
+
+# @lc code=start
+from typing import List
+
+
+class Solution:
+    def makesquare(self, matchsticks: List[int]) -> bool:
+        if len(matchsticks) < 4:
+            return False
+
+        perimeter = sum(matchsticks)
+        side = perimeter // 4
+        if side * 4 != perimeter:
+            return False
+
+        matchsticks.sort(reverse=True)
+        sums = [0 for _ in range(4)]
+
+        def dfs(index):
+            if index == len(matchsticks):
+                return sums[0] == sums[1] == sums[2] == side
+
+            for i in range(4):
+                if sums[i] + matchsticks[index] <= side:
+                    sums[i] += matchsticks[index]
+                    if dfs(index + 1):
+                        return True
+                    sums[i] -= matchsticks[index]
+            return False
+
+        return dfs(0)
+
+
+# @lc code=end
+```
+
 # 2023.9.14
 
 ```python