MinimumPathSum.swift

/**
 * Question Link: https://leetcode.com/problems/minimum-path-sum/
 * Primary idea: Classic Two Dimensionel Dynamic Programming
 * Time Complexity: O(mn), Space Complexity: O(mn)
 */

class MinimumPathSum {
    func minPathSum(_ grid: [[Int]]) -> Int {
        let m = grid.count, n = grid[0].count
        var dp = grid

        for i in 0..<m {
            for j in 0..<n {
                if i == 0 && j == 0 {
                    dp[i][j] = grid[i][j]
                } else if i == 0 {
                    dp[i][j] += dp[i][j - 1]
                } else if j == 0 {
                    dp[i][j] += dp[i - 1][j]
                } else {
                    dp[i][j] += min(dp[i - 1][j], dp[i][j - 1])
                }
            }
        }

        return dp[m - 1][n - 1]
    }
}