LeetCode-in-All

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

class Solution {
    fun minPathSum(grid: Array<IntArray>): Int {
        val m = grid.size
        val n = grid[0].size
        val dp = Array(m) { Array(n) { 0 } }
        for (i in 0 until m) {
            for (j in 0 until n) {
                if (i == 0 && j == 0) {
                    dp[i][j] = grid[i][j]
                } else if (i == 0) {
                    dp[i][j] = dp[i][j - 1] + grid[i][j]
                } else if (j == 0) {
                    dp[i][j] = dp[i - 1][j] + grid[i][j]
                } else {
                    dp[i][j] = minOf(dp[i - 1][j], dp[i][j - 1]) + grid[i][j]
                }
            }
        }
        return dp[m - 1][n - 1]
    }
}

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