reference/#166: 참고 코드 추가

AlgorithmReview/Programmers/Lv3/경주로 건설.swift

@@ -7,36 +7,40 @@
 
 import Foundation
 
-func timeout(_ board:[[Int]]) -> Int {
+func reference(_ board:[[Int]]) -> Int {
 
-    var visit = [[Bool]](repeating: [Bool](repeating: false, count: board.count), count: board.count)
+    let size = board.count
+    var board = board
+    var dp = [[Int]](repeating: [Int](repeating: size*size*500, count: board.count), count: board.count)
     var ans = Int.max
 
-    func valid(_ i: Int, _ j: Int) -> Bool {
-        i < board.count && i >= 0 && j < board.count && j >= 0 && board[i][j] == 0 && !visit[i][j]
-    }
-
-    func move(_ i: Int, _ j: Int, _ d: (Int, Int), _ s: Int, _ c: Int) {
+    func move(_ i: Int, _ j: Int, _ d: (Int, Int), _ cost: Int) {
 
-        if i == board.count-1 && j == board.count-1 {
-            ans = min(ans, 100*s + 500*c); return
-        } else if 100*s + 500*c >= ans {
+        if i == size-1 && j == size-1 {
+            ans = min(ans, cost)
+            return
+        } else if dp[i][j] < cost {
             return
         }
 
-        for coord in [(1,0),(-1,0),(0,1),(0,-1)] {
+        dp[i][j] = cost
+
+        for coord in [(0,1),(1,0),(0,-1),(-1,0)] {
             let row = coord.0 + i, col = coord.1 + j
-            if valid(row, col){
-                visit[row][col] = true
-                let corner = d == coord ? c : c+1
-                move(row,col,coord,s+1,corner)
-                visit[row][col] = false
+            if row < board.count && row >= 0 && col < board.count && col >= 0 && board[row][col] == 0 {
+                board[row][col] = -1
+                if d == coord {
+                    move(row,col,coord,cost+100)
+                } else {
+                    move(row,col,coord,cost+600)
+                }
+                board[row][col] = 0
             }
         }
     }
 
-    visit[0][0] = true
-    move(0,0,(0,0),0,-1)
+    board[0][0] = -1
+    move(0,0,(0,0),0)
 
-    return ans
+    return ans - 500
 }