// 动态规划解决
class Solution {
public:
    int minPathSum(vector<vector<int> >& matrix) {
        int m = matrix.size(), n = matrix[0].size();

        vector<vector<int>> dp(m, vector<int>(n, 0));
        dp[0][0] = matrix[0][0];
        for(int i=1; i<n; i++)    dp[0][i] = dp[0][i-1] + matrix[0][i];
        for(int i=1; i<m; i++)    dp[i][0] = dp[i-1][0] + matrix[i][0];

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