LeetCode "Minimum Path Sum" - 2D DP

class Solution {
public:
int minPathSum(vector<vector<int> > &grid) {
// dp[i][j] = min(dp[i-1][j] + dp[i][j], dp[i][j-1] + dp[i][j]);
int n = grid.size(); // ver
if (n == 0) return 0;
int m = grid[0].size();// hor
if (m == 0) return 0;

//    Init
vector<vector<unsigned long>> dp;
dp.resize(n + 1);
for (int i = 0; i < dp.size(); i++)
dp[i].resize(m + 1);

std::fill(dp[0].begin(), dp[0].end(), std::numeric_limits<int>::max());
for (int i = 0; i <= n; i++) dp[i][0] = std::numeric_limits<int>::max();
dp[1][1] = grid[0][0];

for (int i = 1; i <= n; i ++)
for (int j = 1; j <= m; j++)
{
if (i == 1 && j == 1) continue;
dp[i][j] = std::min(
grid[i - 1][j - 1] + dp[i - 1][j],
grid[i - 1][j - 1] + dp[i][j - 1]
);
}

return dp
[m];
}
};