leetcode 64. 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.

public class Solution {
    public int minPathSum(int[][] grid) {
        if(grid == null || grid.length == 0){
            return 0;
        }
        int m = grid.length;
        int n = grid[0].length;
        int[][] dp = new int[m][n];
        dp[0][0] = grid[0][0];
        
        for(int i=1;i<m;i++){
            dp[i][0] = dp[i-1][0] + grid[i][0];
        }
        
        for(int j=1;j<n;j++){
            dp[0][j] = dp[0][j-1] + grid[0][j];
        }
        
        for(int i=1;i<m;i++){
            for(int j=1;j<n;j++){
                dp[i][j] = Math.min(dp[i-1][j],dp[i][j-1]) + grid[i][j]; 
            }
        }
        return dp[m-1][n-1];
    }
}