HDU1233 - 还是畅通工程 最小生成树,用了三种姿势AC

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int MAXN = 5000;
int Father[MAXN],Ans;
int N,M;
int x,y;
struct Node{
int Now,Next,Len;
}Edge[MAXN];
void Initial()
{
M = (N * (N - 1)) / 2;
Ans = 0;
for(int i = 0;i < MAXN;i++)
Father[i] = i;
}
bool Cmp(Node x,Node y)
{
return x.Len < y.Len;
}
int Find(int x)
{
return x == Father[x] ? x : Father[x] = Find(Father[x]);
}
int main()
{
while(scanf("%d",&N),N)
{
Initial();
for(int i = 1;i <= M;i++)
scanf("%d%d%d",&Edge[i].Now,&Edge[i].Next,&Edge[i].Len);
sort(Edge + 1,Edge + M + 1,Cmp);//注意是从1开始的编号,并按边的长度升序排序
for(int i = 1;i <= M;i++)
{
int xx = Find(Edge[i].Now),yy = Find(Edge[i].Next);
if(xx != yy)
Father[xx] = yy,Ans += Edge[i].Len;
}
printf("%d\n",Ans);
}
return 0;
}
/*用并查集要用到结构体来储存节点和边,适合边少的情况

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int MAXN = 105;
const int Inf = 1<<30;
int Vis[MAXN],Dist[MAXN],Map[MAXN][MAXN],Ans,MIN;
int N,M;
int x,y,z;
void Initial()
{
Ans = 0;
M = (N * (N - 1) / 2);
fill(Vis,Vis + MAXN,0);
memset(Map,0,sizeof(Map));
//	fill(Dist,Dist + MAXN,Inf);
}
void Deal()
{
Vis[1] = 1;
for(int i = 1;i <= N;i++)//假定从编号1开始找
Dist[i] = Map[i][1];
}
void Prim()
{
Deal();
int i,j,k;
for(i = 2;i <= N;i++)
{
k = i;
MIN = Inf;
for(j = 2;j <= N;j++)//找出到A集合的最短距离MIN和编号k
if(!Vis[j] && Dist[j] < MIN)
MIN = Dist[j],k = j;
Ans += MIN;
Vis[k] = 1;//标记
for(j = 2;j <= N;j++)//更新其他点j到A集合的最短距离Dist[j]
if(Map[j][k] < Dist[j])
Dist[j] = Map[j][k];
}
printf("%d\n",Ans);
}
int main()
{
while(scanf("%d",&N),N)
{
Initial();
for(int i = 1;i <= M;i++)
{
scanf("%d%d%d",&x,&y,&z);
Map[x][y] = Map[y][x] = z;//无向图
}
Prim();
}
return 0;
}

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cstring>
using namespace std;
const int MAXN = 105;
const int Inf = 1<<30;
int Vis[MAXN],Dist[MAXN],Map[MAXN][MAXN],Ans,MIN;
int N,M;
int x,y,z;
struct Node{
int v,len;
bool friend operator <(Node x,Node y)
{
return x.len > y.len;
}
};
void Initial()
{
Ans = 0;
M = (N * (N - 1) / 2);
fill(Vis,Vis + MAXN,0);
fill(Dist,Dist + MAXN,Inf);
memset(Map,0,sizeof(Map));
}
void Prim()
{
priority_queue<Node>P;//用优先队列,可以减少一定的运行时间
Node t;
t.v = 1,t.len = 0;
P.push(t);
while(!P.empty())
{
t = P.top();
P.pop();
if(Vis[t.v])continue;
Vis[t.v] = 1;
Ans += t.len;
for(int i = 1;i <= N;i++)
if(!Vis[i] && Map[i][t.v] < Dist[i])
{
Node p;
Dist[i] = Map[i][t.v];
p.v = i,p.len = Map[i][t.v];
P.push(p);
}

}
printf("%d\n",Ans);
}
int main()
{
while(scanf("%d",&N),N)
{
Initial();
for(int i = 1;i <= M;i++)
{
scanf("%d%d%d",&x,&y,&z);
Map[x][y] = Map[y][x] = z;//无向图
}
Prim();
}
return 0;
}