class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int n = grid.size(), m = grid[0].size();
        if (!n) return 0;
        vector<vector<int>> f(n, vector<int>(m, INT_MAX)); //初始化设置为无穷大
        f[0][0] = grid[0][0];
        for (int i = 1; i < n; i ++) f[i][0] = f[i - 1][0] + grid[i][0]; // 初始化第一行，每次只能向右移动
        for (int j = 1; j < m; j ++) f[0][j] = f[0][j - 1] + grid[0][j]; // 初始化第一列，每次只能向下移动

        for (int i = 1; i < n; i ++)
            for (int j = 1; j < m; j ++) 
                f[i][j] = min(f[i - 1][j], f[i][j - 1]) + grid[i][j];
        return f[n - 1][m - 1];
    }
};

yxc代码

class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int n = grid.size(), m = grid[0].size();
        if (!n) return 0;
        vector<vector<int>> f(n, vector<int>(m, INT_MAX)); 
        for (int i = 0; i < n; i ++)
            for (int j = 0; j < m; j ++) {
                if (!i && !j) f[i][j] = grid[i][j];
                else {
                    if (i) f[i][j] = min(f[i][j], f[i - 1][j] + grid[i][j]);
                    if (j) f[i][j] = min(f[i][j], f[i][j - 1] + grid[i][j]);
                }
            }
        return f[n - 1][m - 1];
    }
};