[Leetcode] Minimum Path Sum

class Solution {
public:
    int minPathSum(vector<vector<int> > &mat) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (mat.size() == 0)
            return 0;
        
        int r = mat.size();
        int c = mat[0].size();
        
        for (int i = 1; i < r; ++i)        
            mat[i][0] += mat[i - 1][0];
            
        for (int i = 1; i < c; ++i)        
            mat[0][i] += mat[0][i - 1];
        
        for (int i = 1; i < r; ++i)
        {
            for (int j = 1; j < c; ++j)
            {
                mat[i][j] += min(mat[i - 1][j], mat[i][j - 1]);
            }
        }
        
        return mat[r - 1][c - 1];
    }
};