（Kruskal算法）为什么换了个排序方法就运行不出结果了，求解答

Question

这是原来的正确代码：

#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;

#define MAXVEX 100
struct Edge {
	int begin; 
	int end;
	int weight; 
};
Edge edges[MAXVEX];
char map[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'};

bool cmp(Edge a, Edge b) {
	return a.weight < b.weight;
}

int Find(int *parent, int f) {
	while (parent[f] > 0)
		f = parent[f];
	return f;
}

void Kruskal(Edge edges[], int n, int m) {
	int sum = 0;
	int i,nn,mm;
	int parent[MAXVEX];
	for (i = 0; i < n; ++i) {
		parent[i] = 0;
	}
	for (i = 0; i < m; ++i) {
		nn = Find(parent, edges[i].begin);
		mm = Find(parent, edges[i].end);
		if (nn != mm) {
			parent[nn] = mm;
			cout << map[edges[i].begin] << "->" << map[edges[i].end] << "=" << edges[i].weight << endl;
			sum += edges[i].weight;
		}
	}
	cout << "Minimum weight sum: " << sum << endl;
}


int main() {
	int i,n,m,begin,end,weight;
	cin >> n >> m;
	for (i = 0; i < m; ++i) {
		cin >> begin >> end >> weight;
		edges[i].begin = begin;
		edges[i].end = end;
		edges[i].weight = weight;
	}
	sort(edges, edges + m, cmp);
	Kruskal(edges, n, m); 
	return 0;
}

 

这是我把排序方法改为快速排序后的代码：

#include <iostream>
#include <algorithm>
#include <fstream>
using namespace std;

#define MAXVEX 100
struct Edge 
{
	int begin; 
	int end;
	int weight;//权重 
};
Edge edges[MAXVEX];
char map[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'};

void swap(int *a,int *b)
{
	int t=*a;
	*a=*b;
	*b=t;
	return;
}

void Qsort(int a,int b)
{
	int i,j;
	if(a<b)
	{
		i=a+1;
		j=b;
		while(i<j)
		{
			if(edges[i].weight>edges[a].weight)
			{
				swap(&edges[i].weight,&edges[j].weight);
				j--;
			}
			else
			{
				i++;
			}
		}
		if(edges[i].weight>edges[a].weight)
		{
			i--;
		}
		swap(&edges[i].weight,&edges[a].weight);
		Qsort(a,i);
		Qsort(j,b);
	}
}

int Find(int *parent, int f) 
{
	while (parent[f] > 0)
		f = parent[f];
	return f;
}

void Kruskal(int n, int m) 
{
	int sum = 0;
	int i,nn,mm;
	int parent[MAXVEX];
	for (i = 0; i < n; ++i) 
	{
		parent[i] = 0;
	}
	for (i = 0; i < m; ++i)
	{
		nn = Find(parent, edges[i].begin);
		mm = Find(parent, edges[i].end);
		if (nn != mm) 
		{
			parent[nn] = mm;
			cout << map[edges[i].begin] << "->" << map[edges[i].end] << "=" << edges[i].weight << endl;
			sum += edges[i].weight;
		}
	}
	cout << "Minimum weight sum: " << sum << endl;
}


int main() 
{
	int i,n,m,begin,end,weight;
	cin >> n >> m;
	for (i = 0; i < m; ++i) 
	{
		cin >> begin >> end >> weight;
		edges[i].begin = begin;
		edges[i].end = end;
		edges[i].weight = weight;
	}
	Qsort(0,m-1);
	Kruskal(n, m);
	return 0;
}

我修改后就运行不出结果了，一直找不到错误在哪里，求大佬帮忙解答一下！

Answer 1

有没有大佬救命啊