64. 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.

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