[LeetCode]64 Minimum Path Sum

public class Solution {
public int minPathSum(int[][] grid) {

// Only move down or right.
// Otherwise, -oo

// Validations.
if (grid == null)
return -1; // Invalid input

int m = grid.length;
int n = grid[0].length;

int[][] pathsum = new int[m]
;
for (int i = 0 ; i < m ; i ++)
{
for (int j = 0 ; j < n ; j ++)
{
int v = 0;
if (i == 0 && j == 0)
{
v = grid[i][j];
}
else if (i == 0)
{
v = pathsum[i][j - 1] + grid[i][j];
}
else if (j == 0)
{
v = pathsum[i - 1][j] + grid[i][j];
}
else
{
v = Math.min(pathsum[i][j - 1], pathsum[i - 1][j]) + grid[i][j];
}
pathsum[i][j] = v;
}
}
return pathsum[m - 1][n - 1];
}
}