LeetCode 64 - Minimum Path Sum

Minimum Path Sum

Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers along its path.

Note: You can only move either down or right at any point in time.

My Code

class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size();
        vector<vector<int> > minSum(m, vector<int>(n, 0));

        minSum[0][0] = grid[0][0];
        for (int i = 1; i < m; i++)
            minSum[i][0] = grid[i][0] + minSum[i-1][0];
        for (int j = 0; j < n; j++)
            minSum[0][j] = grid[0][j] + minSum[0][j-1];

        for (int i = 1; i < m; i++)
            for (int j = 1; j < n; j++)
                minSum[i][j] = min(minSum[i-1][j], minSum[i][j-1]) + grid[i][j];

        return minSum[m-1][n-1];
    }
};

Runtime: 33 ms