LeetCode Minimum Path Sum

class Solution {
public:
    int minPathSum(vector<vector<int> > &grid) {
        int rows = grid.size();
        if (rows < 1) return 0;
        int cols = grid[0].size();
        if (cols < 1) return 0;
        
        vector<int> pathsum(cols + 1, INT_MAX);
        pathsum[0] = 0;
        
        for (int i=0; i<rows; i++) {
            for (int j=1; j<=cols; j++) {
                int up = pathsum[j];
                int left = pathsum[j - 1];
                pathsum[j] = grid[i][j - 1];
                if (up > left) {
                    pathsum[j] += left; 
                } else {
                    pathsum[j] += up;
                }
                pathsum[0] = INT_MAX;
            }
        }
        return pathsum[cols];
    }
};

常规DP，这里使用一个一维的DP数组，作用和二维的一致。