baekjoon 20260321

code_study/Baekjoon/swift/2263.swift

@@ -0,0 +1,40 @@
+func main() {
+    guard let n = Int(readLine() ?? "") else { return }
+    guard let line1 = readLine(),
+          let line2 = readLine()
+    else { return }
+    
+    let inOrder = line1.split(separator: " ").compactMap{Int($0)}
+    let postOrder = line2.split(separator: " ").compactMap{Int($0)}
+
+    var inOrderIdx = Array(repeating: -1, count: n+1)
+    
+    for i in 0..<inOrder.count {
+        inOrderIdx[inOrder[i]] = i
+    }
+    
+    var preOrder: [Int] = Array(repeating: 0, count: n)
+    var preIdx = 0
+    
+    func order(inOrder_start si: Int, inOrder_end ei: Int, postOrder_start sp: Int, postOrder_end ep: Int) {
+        if(ei < si || ep < sp) {
+            return
+        }
+        
+        let root = postOrder[ep]
+        let rootIdx = inOrderIdx[root]
+        
+        preOrder[preIdx] = root
+        preIdx += 1
+        
+        let leftLength = rootIdx - si
+        
+        order(inOrder_start: si, inOrder_end: rootIdx - 1, postOrder_start: sp, postOrder_end: sp + leftLength - 1)
+        order(inOrder_start: rootIdx + 1, inOrder_end: ei, postOrder_start: sp + leftLength, postOrder_end: ep - 1)
+    }
+    
+    order(inOrder_start: 0, inOrder_end: n-1, postOrder_start: 0, postOrder_end: n-1)
+    print(preOrder.compactMap({String($0)}).joined(separator: " "))
+}
+
+main()