洛谷P1262间谍网络

题目

我们首先考虑该题没有环应该怎么做,因为没有环所以是一个DAG,因此直接加上入度为0的罪犯,而有环则可以缩点,之后就成为了DAG,然后用一方法做就好了。

\(Code\)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
int n, p, r, top, point, cnt, color, ans, belong[100100], stack[100100], lin[100100], low[100010], dfn[100100], data[100100], vis[100100], minn[100010], in[100100];
// 共有几个间谍,                                             被收买的间谍的值, 
struct edge {
    int from, to, nex;
}e[100100];
inline void add(int f, int t)
{
    e[++cnt].from = f;
    e[cnt].to = t;
    e[cnt].nex = lin[f];
    lin[f] = cnt;
}
void tarjan(int u)
{   
    low[u] = dfn[u] = ++point;
    stack[++top] = u;
    vis[u] = 1;
    for(int i = lin[u]; i; i = e[i].nex)
    {
        int v = e[i].to;
        if(!dfn[v]) tarjan(v), low[u] = min(low[u],low[v]);
        else if(vis[v]) low[u] = min(low[u],dfn[v]); 
    }
    if(low[u] == dfn[u])
    {
        color++; 
        int v = 0;
        while(v != u)
        {
            v = stack[top--];
            vis[v] = 0;
            belong[v] = color;
            minn[color] = min(minn[color], data[v]);
        }
    }
}
int main()
{
    scanf("%d%d", &n, &p);
    for (int i = 1; i <= n; i++)
        data[i] = 2147483647, minn[i] = 2147483647;
    for (int i = 1; i <= p; i++)
    {   
        int a, b;
        scanf("%d%d", &a, &b);
        data[a] = b;
    }
    scanf("%d", &r);
    for (int i = 1; i <= r; i++)
    {
        int a, b;
        scanf("%d%d", &a, &b);
        add(a, b); 
    }
    for (int i = 1; i <= n; i++)
        if (!dfn[i] && data[i] != 2147483647) tarjan(i);
    for (int i = 1; i <= n; i++)
        if (!dfn[i])
            printf("NO\n%d", i), exit(0);   
    printf("YES\n");
    for (int cur = 1; cur <= n; cur++)
        for (int i = lin[cur]; i; i = e[i].nex)     
        {
            int to = e[i].to;
            if (belong[cur] != belong[to])
                in[belong[to]]++;
        }
    for (int i = 1; i <= color; i++)
        if (!in[i])
            ans += minn[i];
    printf("%d", ans);
}   

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转载自www.cnblogs.com/liuwenyao/p/10346930.html
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