51Nod 1212无向图最小生成树

prim

#include<stdio.h>
#include<string.h>
#define inf 0x3f3f3f3f
int G[][];
int vis[],lowc[];
int prim(int G[][],int n){
    int i,j,p,minc,res=;
    memset(vis,,sizeof(vis));//全部初值为0表示没有访问过；
    vis[]=;
    for(i=;i<=n;i++)
        lowc[i]=G[][i];
    for(i=;i<=n;i++){
        minc=inf;
        p=-;
        for(j=;j<=n;j++){
            if(vis[j]==&&lowc[j]<minc)
                {minc=lowc[j];p=j;}
        }
        if(inf==minc) return -;//原图不连通
        res+=minc;
        vis[p]=;
        for(j=;j<=n;j++){//更新lowc[]
            if(vis[j]==&&lowc[j]>G[p][j])
                lowc[j]=G[p][j];
        }
    }
    return res;
}
int main(){
    int n,m;
    int x,y,w;
    while(~scanf("%d %d",&n,&m)){
        memset(G,inf,sizeof(G));
        while(m--){
            scanf("%d%d%d",&x,&y,&w);
            G[x][y]=G[y][x]=w;
        }
        printf("%d\n",prim(G,n));
    }
}

Kruskal

#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<algorithm>
using namespace std;
#define MAX 50005
int father[MAX], son[MAX];
int v, l;    

typedef struct Kruskal //存储边的信息
{
    int a;
    int b;
    int value;
};    

bool cmp(const Kruskal & a, const Kruskal & b)
{
    return a.value < b.value;
}    

int unionsearch(int x) //查找根结点+路径压缩
{
    return x == father[x] ? x : unionsearch(father[x]);
}    

bool join(int x, int y) //合并
{
    int root1, root2;
    root1 = unionsearch(x);
    root2 = unionsearch(y);
    if(root1 == root2) //为环
        return false;
    else if(son[root1] >= son[root2])
        {
            father[root2] = root1;
            son[root1] += son[root2];
        }
        else
        {
            father[root1] = root2;
            son[root2] += son[root1];
        }
    return true;
}    

int main()
{
    int ncase, ltotal, sum, flag;
    Kruskal edge[MAX];
        scanf("%d%d", &v, &l);
        ltotal = , sum = , flag = ;
        for(int i = ; i <= v; ++i) //初始化
        {
            father[i] = i;
            son[i] = ;
        }
        for(int i = ; i <= l ; ++i)
        {
            scanf("%d%d%d", &edge[i].a, &edge[i].b, &edge[i].value);
        }
        sort(edge + , edge +  + l, cmp); //按权值由小到大排序
        for(int i = ; i <= l; ++i)
        {
            if(join(edge[i].a, edge[i].b))
            {
                ltotal++; //边数加1
                sum += edge[i].value; //记录权值之和
                //cout<<edge[i].a<<"->"<<edge[i].b<<endl;
            }
            if(ltotal == v - ) //最小生成树条件：边数=顶点数-1
            {
                flag = ;
                break;
            }
        }
        if(flag) printf("%d\n", sum);
        else printf("data error.\n");
    return ;
}