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