poj-1751 Highways 最小生成树

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题目链接

题意：给定N个城市的坐标，然后下面给出M个已经连接好的城市标号，求他们之间的最小生成树，其中，已连接的话，不必输出。

思路：将已给的城市之间距离标为0，输出的时候，城市之间为零的就不必输出。

#include "stdio.h"#include "string.h"#include "queue"#include "iostream"#include "functional"#include "math.h"#include "algorithm"using namespace std;const int maxn = 855;const int mod = 1000000007 ;const int inf = 1<<30;typedef __int64 LL;typedef pair<double,int> pii;int n,m,ans,mst;double map[maxn][maxn],dis[maxn];int pre[maxn];struct node{int x,y;}city[maxn];double Get_Dis( node a,node b ){return sqrt( ((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y))*1.0 );}int prime( int s ){int ans = 0;priority_queue<pii,vector<pii>,greater<pii> >que;dis[s] = 0;pre[s] = -1;que.push( make_pair( dis[s],s ) );while( !que.empty() ){pii u = que.top(); que.pop();int x = u.second;if( dis[x] != 0 )printf("%d %d\n",x,pre[x]);for( int i = 1; i <= n; i ++ ){if( dis[i] > map[x][i] ){dis[i] = map[x][i];que.push( make_pair( dis[i],i ) );pre[i] = x;}}}return ans;}int main(){#ifndef ONLINE_JUDGE     freopen("data.txt","r",stdin);     #endif  int x,y;while( scanf("%d",&n) != EOF ){for( int i = 1; i <= n; i ++ ){scanf("%d%d",&city[i].x,&city[i].y);dis[i] = inf;}for( int i = 1; i <= n; i ++ ){for( int j = i; j <= n; j ++ ){map[i][j] = map[j][i] = Get_Dis( city[i],city[j] );}}scanf("%d",&m);for( int i = 0; i < m; i ++ ){scanf("%d%d",&x,&y);map[x][y] = map[y][x] = 0;}prime( 1 );}return 0;}

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