典型的动态规划
int minPathSum(vector<vector<int>>& grid) {
if(grid.empty() || grid[0].empty()) return 0;
int row = grid.size();
int col = grid[0].size();
vector<vector<int>> dp(row,vector<int>(col));
dp[0][0] = grid[0][0];
for(int i=1; i<row;++i)
dp[i][0] = dp[i-1][0] + grid[i][0];
for(int j=1; j<col;++j)
dp[0][j] = dp[0][j-1] + grid[0][j];
for(int i=1;i<row;++i)
for(int j=1;j<col;++j)
dp[i][j]=min(dp[i-1][j],dp[i][j-1])+grid[i][j];
return dp[row-1][col-1];
}