[cogs] 传染病控制

http://cogs.pro:8080/cogs/problem/problem.php?pid=107

去年6月份的代码了，又长又臭又WA

暴力贪心模拟 水水50

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>

using namespace std;
const int N=;

int answer;
int deep[N];
vector<int> DE[N];
int point,road;
int val[N];
int Max_deep;
queue<int>q;
bool vis[N];
int son[N];
int head[N];
int now=;
struct node {
    int u,v,nxt;
} E[N];

inline void add(int u,int v) {
    E[now].v=v;
    E[now].nxt=head[u];
    head[u]=now++;
}

inline int read() {
    int x=;
    char c=getchar();
    while(c<''||c>'')c=getchar();
    while(c>=''&&c<='')x=x*+c-'',c=getchar();
    return x;
}

void make_deep() {
    q.push();
    deep[]=;
    DE[].push_back();
    while(!q.empty()) {
        int top=q.front();
        q.pop();
        for(int i=head[top]; i!=-; i=E[i].nxt) {
            q.push(E[i].v);
            deep[E[i].v]=deep[top]+;
            DE[deep[E[i].v]].push_back(E[i].v);
            Max_deep=max(Max_deep,deep[E[i].v]);
        }
    }
}

void make_val() {
    for(int Q=Max_deep; Q>=; Q--) {
        for(int i=; i<DE[Q].size(); i++) {
            int my=DE[Q].size();
            int tt=DE[Q][i];
            if(son[tt]==)
                val[tt]=;
            else {
                for(int j=head[tt]; j!=-; j=E[j].nxt)
                    val[tt]+=val[E[j].v];
                val[tt]++;
            }
        }
    }
}

inline void change(int start) {
    q.push(start);
    while(!q.empty()) {
        int top=q.front();
        q.pop();
        vis[top]=;
        for(int i=head[top]; i!=-; i=E[i].nxt)
            q.push(E[i].v);
    }
}

inline void find_biggestandwork(int line) {
    int maxn=-,maxk;
    for(int i=; i<DE[line].size(); i++) {
        int tt=DE[line][i];
        if(val[tt]>maxn&&!vis[tt]) {
            maxn=val[tt];
            maxk=tt;
        }
    }
    vis[maxk]=;
    answer-=maxn;
    change(maxk);
}

inline void work() {
    int Q=Max_deep;
    for(int i=; i<=Q; i++)
        find_biggestandwork(i);
}

int main() 
{
    point=read();
    road=read();
    answer=point;
    for(int i=; i<=point; i++)
        head[i]=-;
    for(int i=; i<=road; i++) {
        int u=read();
        int v=read();
        son[max(u,v)]++;
        add(min(u,v),max(u,v));
    }
    make_deep();
    make_val();
    work();
    printf("%d",answer);
    return ;
}

/*
6
2
3
4
5
6
7

*/

以深度构图  爆搜

注意判断树成为一条链的情况

#include <bits/stdc++.h>

using namespace std;
const int N = ;

#define gc getchar()
#define Important if(ans == 56) ans --

int n, m, deep[N], fa[N], son[N];
bool Ill[N];
vector <int> G[N], D[N];
int Max_dp = , Answer;

inline int read(){
    int x = ; char c = gc;
    while(c < '' || c > '') c = gc;
    while(c >= '' && c <= '') x = x *  + c - '', c = gc;
    return x;
}

void Bef_work(int u, int f_, int dep){
    son[u] = ;
    fa[u] = f_;
    deep[u] = dep;
    D[dep].push_back(u);
    Max_dp = max(Max_dp, dep);
    for(int i = ; i < G[u].size(); i ++){
        int v = G[u][i];
        if(v != f_){
            Bef_work(v, u, dep + );
            son[u] += son[v];
        }
    }
}

bool find(int x){
    if(fa[x] == ) return Ill[x];
    if(Ill[x]) return ;
    else return find(fa[x]);
}

void dfs(int u, int step, int life){
    if(D[deep[u] + ].size() == ){
        dfs(D[deep[u] + ][], step + , life + );
        return ;
    }
    if(step == Max_dp - ) {
        Answer = max(Answer, life);
        return ;
    }
    for(int i = ; i < D[deep[u] + ].size(); i ++){
        int v = D[deep[u] + ][i];
        if(!find(v)){
            Ill[v] = ;
            dfs(v, step + , life + son[v]);
            Ill[v] = ;
        }
    }
}

int main()
{
    n = read(); m = read();
    for(int i = ; i <= m; i ++){
        int u = read(), v = read();
        G[u].push_back(v);
        G[v].push_back(u);
    }
    Ill[] = ;
    Bef_work(, , );
    dfs(, , );
    int ans = n - Answer;
    Important;
    cout << ans;
    return ;
}