2263번.swift

// 출처 : 백준 트리의 순회
// https://www.acmicpc.net/problem/2263
// 풀이 : hogumachu

let n = Int(readLine()!)!
let inOrder = readLine()!.split(separator: " ").map{Int(String($0))!}
let postOrder = readLine()!.split(separator: " ").map{Int(String($0))!}
var result = ""
var inOrderValueToIndex: [Int:Int] = [:]
var visited = Array(repeating: false, count: n)

for i in 0..<n {
    inOrderValueToIndex[inOrder[i]] = i
}

visit(0, n-1, 0, n-1)

print(result)

func visit(_ infrom: Int, _ inthrough: Int, _ postfrom: Int, _ postthrough: Int) {
    if infrom > inthrough || postfrom > postthrough {
        return
    }
    result += "\(postOrder[postthrough]) "
    let next = inOrderValueToIndex[postOrder[postthrough]]!
    visit(infrom, next - 1, postfrom, postfrom + next - infrom - 1)
    visit(next + 1, inthrough, postfrom + next - infrom, postthrough - 1)

}