1114. Print in Order (Swift version)

main.swift

import Foundation
import Synchronization

// The problem repeats the LC problem '1114. Print in Order'
// https://leetcode.com/problems/print-in-order

// Implement your solution inside the `Foo` class.
// Test with: swift main.swift
final class Foo: Sendable {
    init() {
    }

    func first(_ printFirst: @escaping @Sendable () async -> Void) async {
        await printFirst()  // Don't change this line
    }

    func second(_ printSecond: @escaping @Sendable () async -> Void) async {
        await printSecond()  // Don't change this line
    }

    func third(_ printThird: @escaping @Sendable () async -> Void) async {
        await printThird()  // Don't change this line
    }
}

// MARK: -
// This section is required for the problem testing.
// Do not modify.
for _ in 0..<10_000 {
    await runSolution()
}

func runSolution() async {
    actor Context {
        var str = ""
        func add(_ suffix: String) {
            str += suffix
        }
    }
    let result = await withTaskGroup(of: Void.self) { group in
        let foo = Foo()
        let result = Context()
        for i in [2, 1, 0] {
            group.addTask {
                switch i {
                case 0:
                    await foo.first {
                        await result.add("first")
                    }
                case 1:
                    await foo.second {
                        await result.add("second")
                    }
                case 2:
                    await foo.third {
                        await result.add("third")
                    }
                default:
                    break
                }
            }
        }
        await group.waitForAll()
        return await result.str
    }

    assert(result == "firstsecondthird", "\"\(result)\" != \"firstsecondthird\"")
}