153 - 64 最小路径和

题目

给定一个包含非负整数的 m x n 网格，请找出一条从左上角到右下角的路径，使得路径上的数字总和为最小。

说明：每次只能向下或者向右移动一步。

示例:

输入: [ [1,3,1], [1,5,1], [4,2,1] ] 输出: 7 解释: 因为路径 1→3→1→1→1 的总和最小。

解答

就，思路一样啊

class Solution:
    def minPathSum(self, grid: List[List[int]]) -> int:
        if not grid:
            return 0
        row = len(grid)
        col = len(grid[0])
        for i in range(1, row):
            grid[i][0] += grid[i-1][0]
        for i in range(1, col):
            grid[0][i] += grid[0][i-1]
        for i in range(1, row):
            for j in range(1, col):
                grid[i][j] = min(grid[i-1][j], grid[i][j-1])+grid[i][j]
        return grid[-1][-1]

Runtime: 96 ms, faster than 98.17% of Python3 online submissions for Minimum Path Sum.

Memory Usage: 14.4 MB, less than 77.19% of Python3 online submissions for Minimum Path Sum.

func min(a, b int) int {
    if a < b {
        return a
    }
    return b
}
func minPathSum(grid [][]int) int {
    if grid == nil {
        return 0
    }
    row := len(grid)
    col := len(grid[0])
    for i := 1; i < row; i++ {
        grid[i][0] += grid[i-1][0]
    }
    for i := 1; i < col; i++ {
        grid[0][i] += grid[0][i-1]
    }

    for i := 1; i < row; i++ {
        for j := 1; j < col; j++ {
            grid[i][j] = min(grid[i-1][j], grid[i][j-1]) + grid[i][j]
        }
    }
    return grid[row-1][col-1]
}

Runtime: 12 ms, faster than 20.00% of Go online submissions for Minimum Path Sum.

Memory Usage: 3.9 MB, less than 100.00% of Go online submissions for Minimum Path Sum.

var minPathSum = function(grid) {
  if (!grid) {
    return 0
  }
  row = grid.length
  col = grid[0].length
  for (let i = 1; i < row; i++) {
    grid[i][0] += grid[i - 1][0]
  }
  for (let i = 1; i < col; i++) {
    grid[0][i] += grid[0][i - 1]
  }
  for (let i = 1; i < row; i++) {
    for (let j = 1; j < col; j++) {
      grid[i][j] = Math.min(grid[i - 1][j], grid[i][
        j -
        1
      ]) + grid[i][j]
    }
  }
  return grid[row - 1][col - 1]
}

Runtime: 68 ms, faster than 22.45% of JavaScript online submissions for Minimum Path Sum.

Memory Usage: 35.8 MB, less than 66.67% of JavaScript online submissions for Minimum Path Sum.