Question

我只运行一个简单的代码，但我一直得到＆＃34;处理完成后退出代码139（被信号11中断：SIGSEGV）＆＃34; 做一些调试，我发现edge [0] .start的值以某种方式变成了-2147483644。我发现这种行为很难解释，仍然试图找到我错在哪里，但我甚至不更新任何边缘值！无论如何，无论你给我什么提示都会受到极大的重视。你会发现下面的代码。提前致谢！温馨的祝福

#include <stdio.h>
#include <climits>
#include "Utils.h"

struct edge {
    int start;
    int end;
    int weight;
};

int main() {
    int n = 4;
    int m = 4;
    edge edges[4] = {
            {2,4,5},
            {4,1,6},
            {1,3,8},
            {3,2,-3}
    };
    int v,e;
    int distance[4];
    // Step 1: initialize graph
    for(v = 0; v < n; v++){
        distance[v] = INT_MAX;
    }
    distance[0] = 0; //source

    // Step 2: relax edges repeatedly
    for(v = 0; v < n; v++){
        for(e = 0; e < m; e++){
            if(distance[edges[e].start] + edges[e].weight < distance[edges[e].end] ){ //relax
                distance[edges[e].end] = distance[edges[e].start] + edges[e].weight;
            }
        }
    }
    // Step 3: check for negative-weight cycles
    for(e = 0; e < m; e++) {
        if (distance[edges[e].start] + edges[e].weight < distance[edges[e].end]) { //shouldn't be able to relax
            std::cout << "Negative cycle detected, please declare war to Paraguay";
        }
    }
    for(v = 0; v < n; v++){
        std::cout << distance[v] << std::endl;
    }
    return 0;
}

Answer 1

你的＆＃39; n＆＃39;和＆＃39; m＆＃39;迭代器变量定义为4，但是＆＃39; edge＆＃39;数组的索引介于0和3之间。您的循环将尝试访问边[4]，导致索引超出范围和未定义的行为，这可能是您的起始值损坏的原因。

Answer 2

您已定义距离变量，大小为4

int distance[4];

边缘数组的值为：

 edge edges[4] = {
            {2,4,5},
            {4,1,6},
            {1,3,8},
            {3,2,-3}
    };

您使用edge structure的值访问每个distance array.的单元格边缘的值范围为-3到8，而距离的值范围为0到3;这将导致缓冲区溢出并导致应用程序崩溃。

Answer 3

我实际上不知道为什么，但这对我有用：

auto menu = Menu::create(menuButton,moreButton, NULL);

而不是使用#include <iostream> struct edge { int start; int end; int weight; }; int main() { int n = 4; int m = 4; const edge edges[4] = { {2,4,5}, {4,1,6}, {1,3,8}, {3,2,-3} }; /* <= for my surprise, I'm not get error with this * for indexes of distance[something] */ int v,e; int distance[4]; // Step 1: initialize graph for(v = 0; v < n; v++){ distance[v] = 214748364; // <== with this get fixed } distance[0] = 0; //source // Step 2: relax edges repeatedly for(v = 0; v < n; v++){ for(e = 0; e < m; e++){ if(distance[edges[e].start] + edges[e].weight < distance[edges[e].end] ){ //relax distance[edges[e].end] = distance[edges[e].start] + edges[e].weight; } } } // Step 3: check for negative-weight cycles for(e = 0; e < m; e++) { if (distance[edges[e].start] + edges[e].weight < distance[edges[e].end]) { //shouldn't be able to relax std::cout << "Negative cycle detected, please declare war to Paraguay"; } } for(v = 0; v < n; v++){ std::cout << distance[v] << std::endl; } return 0; }，只需使用distance[v] = INT_MAX;或不太接近distance[v] = 214748364;的内容，我就会得到此输出：

INT_MAX

c ++ struct value似乎在它自己的基础上发生变化

3 个答案: