Leetcode 之 Minimum Path Sum

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.

Note: You can only move either down or right at any point in time.

跟之前一样，用DP来算到每个点的最短路径。递推公式如下：
f(i,j) = min( f(i,j-1), f(i-1,j)) + grid[i][j]

注意，第0行和第0列这时候要从[0][0]点开始根据grid数组计算了。另外，数组从0开始，下标-1要记住。

public int minPathSum(int[][] grid) {        int n = grid.length;        int m = grid[0].length;        if(n == 0 || m == 0)    return 0;        int[][] f = new int[n][m];        for(int i = 0;i < n;i++){            for(int j = 0;j < m;j++){                if(i == 0 && j >= 1){                    f[0][j] = f[0][j - 1] + grid[i][j];                }                else if(j == 0 && i >= 1){                    f[i][0] = f[i - 1][0] + grid[i][j];                }                else if(i == 0 && j == 0){                    f[0][0] = grid[0][0];                }                else  f[i][j] = Math.min(f[i - 1][j], f[i][j - 1]) + grid[i][j];            }        }        return f[n - 1][m - 1];    }

61 / 61 test cases passed.
Status: Accepted
Runtime: 328 ms