Swift Playground 错误 - BAD_INSTRUCTION

Question

Swift Playground 错误 - BAD_INSTRUCTION

4

我有以下贪心算法，但是它给了我以下错误：

Playground 执行中止：错误：执行被中断，原因：EXC_BAD_INSTRUCTION（code=EXC_I386_INVOP，subcode=0x0）。进程已停留在中断点处，请使用“thread return -x”返回表达式评估之前的状态。

类：

// This class represents an undirected graph using adjacency list
public class Graph{
    var V: Int // number of vertices
    var adj: [[Int]] = [[]] //Adjacency List

    public init(v: Int) {
        V = v
        adj = [[Int]](repeating: [], count: v)
    }

    // Function to add an edge into the graph
    public func addEdge(v: Int, w: Int){
        adj[v].append(w)
        adj[w].append(v) // Graph is undirected
    }

    // Assigns colors (starting from 0) to all vertices and
    // prints the assignment of colors
    public func greedyColoring() {
        var result = [Int]()

        //Assign the first color to first vertex
        result[0] = 0

        //Initialize the remaining V-1 vertices as unassigned
        for i in 0 ..< V{
            //No Color is assigned
            result[i] = -1
        }

        // A temporary array to store the available colors. True
        // value of available[cr] would mean that the color cr is
        // assigned to one of its adjacent vertices
        var available = [Bool]()
        for cr in 0 ..< V{
            available[cr] = false
        }

        // Assign colors to remaining V-1 vertices
        for i in 1 ..< V{
            //Process all adjacent vertices and flag their colors as unavailable
            for un in 0 ..< adj[i].count{
                if result[un] != -1 {
                    available[result[un]] = true
                }
            }

            //find the first available color
            for cr in 0 ..< V{
                if available[cr] == false{
                    result[i] = cr
                    break
                }
            }

            //Reset the values back to false for the next iteraation
            for un in 0 ..< adj[i].count{
                if result[un] != -1 {
                    available[result[un]] = true
                }
            }
        }

        //Print result
        for r in 0 ..< V{
            print("Vertex \(r) --> Color \(result[r])")
        }
    }
}

这是我称呼它的方式：

import Foundation
import UIKit
import XCPlayground

var g1 = Graph(v: 5)
g1.addEdge(v: 0, w: 1)
g1.addEdge(v: 0, w: 2)
g1.addEdge(v: 1, w: 2)
g1.addEdge(v: 1, w: 3)
g1.addEdge(v: 2, w: 3)
g1.addEdge(v: 3, w: 4)
g1.greedyColoring() // Fails HERE

前些时间我在代码中遇到了一些错误，这些错误与我如何使用数组有关。为什么Playground没有给出像 “下标越界” 这样的明确错误？我的Debug控制台没有任何输出...是什么导致了我的代码错误呢？

- SaifDeen

2个回答

1

只需编写：

import PlaygroundSupport

它帮助了我

- Janserik

似乎这是游乐场错误的正确解决方案，无论您拥有什么代码。 - DionizB

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- chengsam · Accepted Answer

在此代码片段中：

var result = [Int]()

//Assign the first color to first vertex
result[0] = 0

数组result为空，因此您无法通过result[0]访问第一个元素。

解决方案：

更改为：

var result = [Int]()

//Assign the first color to first vertex
result[0] = 0

//Initialize the remaining V-1 vertices as unassigned
for i in 0 ..< V{
    //No Color is assigned
    result[i] = -1
}

// A temporary array to store the available colors. True
// value of available[cr] would mean that the color cr is
// assigned to one of its adjacent vertices
var available = [Bool]()
for cr in 0 ..< V{
    available[cr] = false
}

致：

var result = [Int]()

//Assign the first color to first vertex
result.append(0)

//Initialize the remaining V-1 vertices as unassigned
for _ in 0 ..< V{
    //No Color is assigned
    result.append(-1)
}

// A temporary array to store the available colors. True
// value of available[cr] would mean that the color cr is
// assigned to one of its adjacent vertices
var available = [Bool]()
for _ in 0 ..< V{
    available.append(false)
}