【LeetCode】120.三角形最小路径和

• 最优子结构的典型例题了

1.题目

2.分析

用dp的方法解决这道题。

3.代码

class Solution:
    def minimumTotal(self, triangle: List[List[int]]) -> int:
        n = len(triangle)
        dp  = [[0] * n for i in range(n)]
        # print(dp)
        dp[0][0] = triangle[0][0]
        for i in range(1,n):
            for j in range(i+1):
                if j ==0:# 无法从左上角推导
                    dp[i][j] = dp[i-1][j] + triangle[i][j]
                    continue
                    
                if j!=i: 
                    dp[i][j] = min(dp[i-1][j-1],dp[i-1][j]) + triangle[i][j]
                else: # 只能从左上角推导
                    dp[i][j] = dp[i-1][j-1] + triangle[i][j]
        # print(dp)
        return min(dp[n-1])