Refactor solution to Minimum Path Sum

DP/MinimumPathSum.swift

@@ -6,27 +6,23 @@
 
 class MinimumPathSum {
     func minPathSum(_ grid: [[Int]]) -> Int {
-        guard grid.count != 0 && grid[0].count != 0 else{
-            return 0
-        }
-
         let m = grid.count, n = grid[0].count
-        var dp = Array(repeating: Array(repeating: 0, count: n), count: m)
-        
+        var dp = grid
+
         for i in 0..<m {
             for j in 0..<n {
-                if i == 0 && j == 0{
+                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]
+                    dp[i][j] += dp[i][j - 1]
                 } else if j == 0 {
-                    dp[i][j] = dp[i - 1][j] + grid[i][j]
+                    dp[i][j] += dp[i - 1][j]
                 } else {
-                    dp[i][j] = min(dp[i][j - 1], dp[i - 1][j]) + grid[i][j]
+                    dp[i][j] += min(dp[i - 1][j], dp[i][j - 1])
                 }
             }
         }
-        
+
         return dp[m - 1][n - 1]
     }
-}
+}