标签：c   图论   强连通   

Summer Holiday

12 16
2 2 2 2 2 2 2 2 2 2 2 2 
1 3
3 2
2 1
3 4
2 4
3 5
5 4
4 6
6 4
7 4
7 12
7 8
8 7
8 9
10 9
11 10

3 6

不想写解析了，偷偷粘过来阿宇的解析

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#define maxn 1000 + 100
#define maxm 2000 + 200
#define INF 0x3f3f3f3f
using namespace std;
int n, m;
struct node{
    int u, v, next;
};
int head[maxn], cnt;

node edge[maxm];
int low[maxn], dfn[maxn];
int dfs_clock;
int Stack[maxn], top;
bool InStack[maxn];
int Belong[maxn];
int scc_clock;
int cost[maxn];//通知每个人的花费
int in[maxn];//每个【缩点】的入度
vector<int>scc[maxn];

void init(){
    cnt = 0;
    memset(head, -1, sizeof(head));
}

void addedge(int u, int v){
    edge[cnt] = {u, v, head[u]};
    head[u] = cnt++;
}

void getmap(){
    for(int i = 1; i <= n; ++i)
        scanf("%d", &cost[i]);
    while(m--){
        int a, b;
        scanf("%d%d", &a, &b);
        addedge(a, b);
    }
}

void Tarjan(int u, int per){
    int v;
    dfn[u] = low[u] = ++dfs_clock;
    Stack[top++] = u;
    InStack[u] = true;
    for(int i = head[u]; i != -1; i = edge[i].next){
        v = edge[i].v;
        if(!dfn[v]){
            Tarjan(v, u);
            low[u] = min(low[u], low[v]);
        }
        else if(InStack[v]){
            low[u] = min(low[u], dfn[v]);
        }
    }
    if(dfn[u] == low[u]){
        scc_clock++;
        scc[scc_clock].clear();
        do{
            v = Stack[--top];
            InStack[v] = false;
            Belong[v] = scc_clock;
            scc[scc_clock].push_back(v);
        }while(v != u);
    }
}

void suodian(){//缩点
    memset(in, 0, sizeof(in));
    for(int i = 0; i < cnt; i++){
        int u = Belong[edge[i].u];
        int v = Belong[edge[i].v];
        if(u != v)
            in[v]++;
    }
}

void find(){
    memset(dfn, 0, sizeof(dfn));
    memset(low, 0, sizeof(low));
    memset(Stack, 0, sizeof(Stack));
    memset(Belong, 0, sizeof(Belong));
    memset(InStack, false, sizeof(InStack));
    dfs_clock = scc_clock = top = 0;
    for(int i = 1; i <= n; ++i){//不是连通图
        if(!dfn[i])
            Tarjan(i, i);
    }
}

void solve(){
    int ans = 0;
    int sum = 0;
    for(int i = 1; i <= scc_clock; ++i){
        if(in[i] == 0){
            //printf("--%d\n", i);
            ans++;
            int mins = INF;
            for(int j = 0; j < scc[i].size(); ++j)
                mins = min(mins, cost[scc[i][j]]);
            sum += mins;
        }
    }
    printf("%d %d\n", ans, sum);
}

int main (){
    while(scanf("%d%d", &n, &m) != EOF){
        init();
        getmap();
        find();
        suodian();
        solve();
    }
    return 0;
}

HDU 1827--Summer Holiday【强连通缩点新建图】

标签：c   图论   强连通   

原文地址：http://blog.csdn.net/hpuhjh/article/details/47777649