LeetCode-in-Rust

64. Minimum Path Sum

Medium

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

Solution

impl Solution {
    pub fn min_path_sum(grid: Vec<Vec<i32>>) -> i32 {
        let (w, h) = (grid.len(), grid[0].len());
        let mut dp = vec![vec![0; h]; w];
        
        for i in 0..w {
            for j in 0..h {
                if i == 0 && j == 0 {
                    dp[i][j] = grid[i][j];
                } else if j == 0 {
                    dp[i][j] = grid[i][j] + dp[i-1][j];
                } else if i == 0 {
                    dp[i][j] = grid[i][j] + dp[i][j-1];
                } else {
                    dp[i][j] = grid[i][j] + std::cmp::min(dp[i-1][j], dp[i][j-1]);
                }
            }
        }

        dp[w-1][h-1]
    }
}

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