【前向星】数据结构的实现

/*
	前向星数据结构的实现
	2014-4-1 21:36:48
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <algorithm>
#define MAX 10000
using namespace std;

int head[MAX]; //存储起点为Vi的第一条边的位置
struct NODE{
	int from, to, w; //起点，终点，权值
};
NODE edge[MAX];

bool cmp(NODE a, NODE b){
	if(a.from == b.from && a.to == b.to) return a.w < b.w;
	if(a.from == b.from) return a.to < b.to;
	return a.from < b.from;
}

int main(){
	int n, m; //n个点，m个数据
	
	scanf("%d%d", &n, &m);
	
	for(int i = 0; i < m; ++i)
		scanf("%d%d%d", &edge[i].from , &edge[i].to, &edge[i].w);
	sort(edge, edge + m, cmp); //排序
	memset(head, -1, sizeof(head));
	head[edge[0].from] = 0;
	for(int i = 1; i < m; ++i)
		if(edge[i].from != edge[i - 1].from)
			head[edge[i].from] = i;
	
	//遍历
	for(int i = 1; i <= n; ++i){
		for(int k = head[i]; edge[k].from == i && k < m; ++k)
			printf("%d %d %d\n", edge[k].from, edge[k].to, edge[k].w);
	}	
	system("pause");
	return 0;
}