POJ1797 Heavy Transportation （最短路径/最小生成树kruskal)

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>

using namespace std;

int p[1005];//集合的数组
int r[1005];//按秩

int m, n;
//
int find(int v)
{
if(v != p[v])
p[v] = find(p[v]);
return p[v];
}

void join(int u, int v)
{
int a = find(u);
int b = find(v);
if(a == b)
return;
if(r[a] < r[b])
{
p[a] = b;
}
else if(r[a] > r[b])
{
p[b] = a;
}
else
{
p[a] = b;
r[b] ++;
}
}

void init_set()
{
int i;
for(i = 1; i <= n; i++)
{
p[i] = i;
r[i] = 1;
}
}

struct Edge
{
int u;
int v;
int weight;
};

struct Edge edge[1000005];

void quick_sort(struct Edge * start, struct Edge * end)
{
if(start >= end)
return;
struct Edge* loc = start;
struct Edge* iterator;
struct Edge tmp;
for(iterator = start; iterator != end; iterator++)
{
if(iterator -> weight < (end - 1) -> weight) //按从小到大的顺序排列， 决定是最小还是
{
tmp = *loc;
*loc = *iterator;
*iterator = tmp;

loc++;
}
}
tmp = *loc;
*loc = *(end - 1);
*(end - 1) = tmp;

quick_sort(start, loc);
quick_sort(loc + 1, end);
}

bool cmp(Edge e1, Edge e2)
{
return e1.weight > e2.weight;
}

int kru()
{
init_set();
//quick_sort(edge, edge+m);
sort(edge, edge + m, cmp);
int i;
for(i = 0; i < m; i++)
{
int u = edge[i].u;
int v = edge[i].v;
//如果两个顶点不在一个集合中，则不会生成环，于是该边被加入生成树
if(find(u) != find(v))
{
join(u, v);
}
if(find(1) == find(n))
{
return edge[i].weight;
}
}
return edge[i].weight;
}

void ace()
{
int Case, no = 1;
int ret, i;
//freopen("test.txt", "r", stdin);
scanf("%d", &Case);
for(no = 1; no <= Case; no++)
{
scanf("%d%d", &n, &m);
for(i = 0; i < m; i++)
{
scanf("%d%d%d", &edge[i].u, &edge[i].v, &edge[i].weight);
}
ret = kru();
printf("Scenario #%d:\n%d\n\n", no, ret);
}
}

int main()
{
ace();
return 0;
}