HDU 1102

最小生成树

对于必须要加入的边， 让其边权为0 即可

Prim ：

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
const int maxn = 100 + 31;
const int INF=0x3f3f3f3f;
int Map[maxn][maxn];
int Vis[maxn], Dis[maxn];
int ans;
int n;
void Prim()
{
    int k;
    for(int i = 1; i <= n; ++i)
        Dis[i] = Map[1][i], Vis[i] = 0;
    Dis[1] = 0;
    Vis[1] = 1;
    for(int i = 1; i <= n; ++i)
    {
        int tmp = INF;
        for(int j = 1; j <= n; ++j)
            if(Vis[j] == 0 && tmp > Dis[j]) tmp = Dis[j], k = j;
        if(tmp == INF) break;
        Vis[k] = 1;
        ans += Dis[k];
        for(int j = 1; j <= n; ++j)
            if(Vis[j] == 0 && Dis[j] > Map[k][j]) Dis[j] = Map[k][j];
    }
}

int main()
{
    while(~scanf("%d",&n))
    {
        ans = 0;
        //memset(Map,INF,sizeof(Map));
        for(int i = 1; i <= n; ++i)
            for(int j = 1; j <= n; ++j)
            scanf("%d",&Map[i][j]);
        int q,a,b;
        scanf("%d",&q);
        while(q--)
        {
            scanf("%d%d",&a,&b);
            Map[a][b] = Map[b][a] = 0;
        }
        Prim();
        printf("%d\n",ans);
    }
    return 0;
}

\

Kruskal ：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
using namespace std;
const int maxn = 100 + 7;
struct Edges{
    int u, v;
    int val;
}edges[maxn * maxn];
int Pre[maxn];
int n,cnt,ans;

void Add_Edge(int u,int v,int val)
{
    edges[cnt].u = u, edges[cnt].v = v, edges[cnt].val = val;
    cnt ++;
}

void Init()
{
    for(int i = 0; i < maxn ; ++i) Pre[i] = i;
    cnt = 0;
    ans = 0;
}

int Find(int x)
{
    int r = x;
    while(r != Pre[r]) r = Pre[r];
    return Pre[x] = r;
}

bool Union(int x,int y)
{
    int ax = Find(x), ay = Find(y);
    if(ax == ay) return false;
    Pre[ax] = ay;
    return true;
}

bool cmp(Edges a, Edges b)
{
    return a.val < b.val;
}

void Kruskal()
{
    sort(edges,edges+cnt,cmp);
    for(int i = 0; i < cnt; ++i)
    {
        if(Union(edges[i].u,edges[i].v)) ans += edges[i].val;
    }
}

int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        Init();
        int a, b, q;
        for(int i = 1; i <= n; ++i)
            for(int j = 1; j <= n; ++j)
            {
                scanf("%d",&a);
                Add_Edge(i,j,a);
            }
        scanf("%d",&q);
        while(q--)
        {
            scanf("%d%d",&a,&b);
            a = Find(a);
            b = Find(b);
            Pre[a] = b;
        }
        Kruskal();
        printf("%d\n",ans);
    }
    return 0;
}

第一道最小生成树，纪念一下。。