模板（最短路，最小生成树，并查集）

Posted 2020-09-09 Alex丶Baker

单源最短路

#include<queue>
#include<cstdio>

#define INF 2147483647LL

using namespace std;

struct node {
    int to,dis,next;
};
struct node edge[500005];

int n,m,num,head[10001],dis_1[10001];

inline void edge_add(int from,int to,int dis)
{
    num++;
    edge[num].to=to;
    edge[num].dis=dis;
    edge[num].next=head[from];
    head[from]=num;
}

void SPFA(int start)
{
    queue<int>que;
    bool if_in_spfa[10001];
    for(int i=1;i<=n;i++) dis_1[i]=INF,if_in_spfa[i]=false;
    dis_1[start]=0,if_in_spfa[start]=true;
    que.push(start);
    while(!que.empty())
    {
        int cur_1=que.front();
        que.pop();
        for(int i=head[cur_1];i;i=edge[i].next)
        {
            if(dis_1[cur_1]+edge[i].dis<dis_1[edge[i].to])
            {
                dis_1[edge[i].to]=edge[i].dis+dis_1[cur_1];
                if(!if_in_spfa[edge[i].to])
                {
                    if_in_spfa[edge[i].to]=true;
                    que.push(edge[i].to);
                }
            }
        }
        if_in_spfa[cur_1]=false;
    }
}

int main()
{
    int s;
    scanf("%d%d%d",&n,&m,&s);
    int from,to,dis;
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&from,&to,&dis);
        edge_add(from,to,dis);
    }
    SPFA(s);
    for(int i=1;i<=n;i++) printf("%d ",dis_1[i]);
    return 0;
}

 

最小生成树

#include<cstdio>
#include<algorithm>

using namespace std;

struct node {
    int from,to,dis;
};
struct node edge[200001];

int num_head,num_edge,f[5001],num_2=0;

int find(int x)
{
    if(f[x]==x) return x;
    else return f[x]=find(f[x]);
}

inline void edge_add(int from,int to,int dis)
{
    num_2++;
    edge[num_2].to=to;
    edge[num_2].dis=dis;
    edge[num_2].from=from;
}

bool cmp(struct node a,struct node b){return a.dis<b.dis;}

int main()
{
    scanf("%d%d",&num_head,&num_edge);
    int from,to,dis;
    for(int i=1;i<=num_edge;i++)
    {
        scanf("%d%d%d",&from,&to,&dis);
        edge_add(from,to,dis);
    }
    for(int i=1;i<=num_head;i++) f[i]=i;
    sort(edge+1,edge+num_edge+1,cmp);
    int head_1=0,num_1=0,sum=0;
    while(num_1<num_edge)
    {
        num_1++;
        int x=find(edge[num_1].from),y=find(edge[num_1].to);
        if(x!=y)
        {
            sum+=edge[num_1].dis;
            head_1++;
            f[x]=y;
        }
        if(head_1==num_head-1) break;
    }
    if(head_1==num_head-1) printf("%d\n",sum);
    else printf("orz\n");
    return 0;
}

并查集

#include<cstdio>

using namespace std;

int n,m,f[10001];

int find(int x)
{
    if(f[x]==x) return x;
    else return f[x]=find(f[x]);
}

int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) f[i]=i;
    int now_1,now_2,cur_1;
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&cur_1,&now_1,&now_2);
        now_1=find(now_1),now_2=find(now_2);
        if(cur_1==1) f[now_1]=now_2;
        else now_1==now_2?printf("Y\n"):printf("N\n");
    }
    return 0;
}