120. 三角形最小路径和

原题

https://leetcode.cn/problems/triangle/description/

思路

动态规划

复杂度

时间：O(n²)
空间：O(n²)

Python代码

class Solution:
    def minimumTotal(self, triangle: List[List[int]]) -> int:
        dp = triangle[:]
        for i in range(1, len(triangle)):
            for j in range(len(triangle[i])):
                if j == 0:
                    dp[i][j] = dp[i - 1][j] + dp[i][j]
                elif j == len(triangle[i])-1:
                    dp[i][j] = dp[i - 1][j-1] + dp[i][j]
                else:
                    dp[i][j] = min(dp[i-1][j-1], dp[i-1][j]) + dp[i][j]
        return min(dp[-1])

Go代码

func minimumTotal(triangle [][]int) int {
	// 将triangle复制给dp
	dp := make([][]int, len(triangle))
	for i := 0; i < len(dp); i++ {
		dp[i] = make([]int, len(triangle[i]))
		copy(dp[i], triangle[i])
	}
	for i := 1; i < len(triangle); i++ {
		for j := 0; j < len(triangle[i]); j++ {
			if j == 0 {
				dp[i][j] = dp[i-1][j] + dp[i][j]
			} else if j == len(triangle[i])-1 {
				dp[i][j] = dp[i-1][j-1] + dp[i][j]
			} else {
				dp[i][j] = min(dp[i-1][j-1], dp[i-1][j]) + dp[i][j]
			}
		}
	}
	sort.Ints(dp[len(dp)-1])
	return dp[len(dp)-1][0]
}