拓扑排序Swift

import Foundation

func topologicalSort(_ graph: [Int: [Int]]) -> [Int] {
    var inDegree = [Int: Int]()
    var result = [Int]()

    for (node, neighbors) in graph {
        for neighbor in neighbors {
            inDegree[neighbor, default: 0] += 1
        }
    }

    var queue = [Int]()
    for (node, _) in graph {
        if inDegree[node] == nil {
            queue.append(node)
        }
    }

    while !queue.isEmpty {
        let node = queue.removeFirst()
        result.append(node)

        if let neighbors = graph[node] {
            for neighbor in neighbors {
                inDegree[neighbor]! -= 1
                if inDegree[neighbor]! == 0 {
                    queue.append(neighbor)
                }
            }
        }
    }

    return result
}

// 使用示例
let graph = [
    1: [2, 3],
    2: [4],
    3: [4, 5],
    4: [],
    5: []
]

let sortedNodes = topologicalSort(graph)
print(sortedNodes) // 输出: [1, 3, 2, 5, 4]