0064. Minimum Path Sum

https://leetcode.com/problems/minimum-path-sum

Description

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.

Example 1:

**Input:** grid = [[1,3,1],[1,5,1],[4,2,1]]
**Output:** 7
**Explanation:** Because the path 1 → 3 → 1 → 1 → 1 minimizes the sum.

Example 2:

**Input:** grid = [[1,2,3],[4,5,6]]
**Output:** 12

Constraints:

• m == grid.length

• n == grid[i].length

• 1 <= m, n <= 200

• 0 <= grid[i][j] <= 100

ac

class Solution {
    public int minPathSum(int[][] grid) {
        // edge cases
        if (grid == null || grid.length == 0 || grid[0].length == 0) 
            return 0;

        int row = grid.length;
        int col = grid[0].length;
        // init
        for (int r = 1; r < row; r++) {
            grid[r][0] += grid[r-1][0];
        }
        for (int c = 1; c < col; c++) {
            grid[0][c] += grid[0][c-1];
        }

        for (int r = 1; r < row; r++) {
            for (int c = 1; c < col; c++) {
                grid[r][c] += Math.min(grid[r-1][c], grid[r][c-1]);
            }
        }

        return grid[row-1][col-1];
    }
}