leetcode.com 312. Burst Balloons

문제 링크: https://leetcode.com/problems/burst-balloons/description/

Author: skysign

leetcode.com 312. Burst Balloons/main.py

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+from typing import List
+import sys
+
+
+# N ** 3으로 작성된 코드
+# def maxCoins(self, nums: List[int]) -> int:
+#     n = len(nums)
+#     nums = [1] + nums + [1]
+#     dp = [[0] * (n + 2) for _ in range(n + 2)]
+#
+#     for i in range(n, 0, -1):
+#         for j in range(i, n + 1):
+#             for k in range(i, j + 1):
+#                 dp[i][j] = max(dp[i][j], dp[i][k - 1] + dp[k + 1][j] + nums[k] * nums[i - 1] * nums[j + 1])
+#
+#     return dp[1][n]
+
+class Solution:
+    def maxCoins(self, nums: List[int]) -> int:
+        nums = [1] + nums + [1]
+        l = len(nums)
+        dp = [[-1] * l for _ in range(l)]
+
+        def dp_d_c(i_left, i_right):
+            if i_right - i_left < 0:
+                return 0
+
+            if dp[i_left][i_right] > -1:
+                return dp[i_left][i_right]
+
+            coins_mx = 0
+
+            for i in range(i_left, i_right + 1):
+                coins_i = nums[i_left - 1] * nums[i] * nums[i_right + 1]
+                coins_lr = 0
+                coins_lr += dp_d_c(i_left, i - 1)
+                coins_lr += dp_d_c(i + 1, i_right)
+
+                coins_mx = max(coins_mx, coins_i + coins_lr)
+
+            dp[i_left][i_right] = coins_mx
+
+            return dp[i_left][i_right]
+
+        coins = dp_d_c(1, l - 2)
+        return coins
+
+# DP (Naive)
+# def maxCoins(self, nums: List[int]) -> int:
+#     memo: dict = {}
+#     nums = [1] + nums + [1]
+#     coins = self.dp(nums, memo)
+#
+#     return coins
+#
+# def dp(self, nums: List[int], memo: dict):
+#     if tuple(nums) in memo.keys():
+#         return memo[tuple(nums)]
+#
+#     if len(nums) == 3:
+#         memo[tuple(nums)] = nums[0] * nums[1] * nums[2]
+#         return memo[tuple(nums)]
+#
+#     coins = 0
+#     mx = -sys.maxsize - 1
+#
+#     for i in range(1, len(nums) - 1):
+#         coins = nums[i - 1] * nums[i] * nums[i + 1]
+#         coins_2 = self.dp(nums[:i] + nums[i + 1:], memo)
+#
+#         mx = max(mx, coins + coins_2)
+#
+#     memo[tuple(nums)] = mx
+#
+#     return mx

leetcode.com 312. Burst Balloons/test_main.py

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+from unittest import TestCase
+from main import Solution
+
+
+class TestSolution(TestCase):
+    def test1_max_coins(self):
+        sol = Solution()
+        self.assertEqual(167, sol.maxCoins(nums=[3, 1, 5, 8]))
+
+    def test2_max_coins(self):
+        sol = Solution()
+        self.assertEqual(10, sol.maxCoins(nums=[1, 5]))