2020CCPC秦皇岛 J - Kingdom‘s Power

Posted 2022-12-11 solemntee

#include<bits/stdc++.h>
using namespace std;
vector<int>v[1000005];
int siz[1000005],dep[1000005];
int dp[2][1000005];
void dfs1(int x,int pre)

    siz[x]=1;
    if(x!=1)dep[x]=dep[pre]+1;
    for(auto to:v[x])if(to!=pre)
    
        dfs1(to,x);
        siz[x]+=siz[to];
    


void dfs(int x,int pre)


    dp[0][x]=siz[x]*2;
    if((int)v[x].size()==1&&x!=1)
    
        dp[1][x]=dep[x];
        return;
    
    bool flag=false;
    int ans=0;
    int mn=1000000;
    for(auto to:v[x])if(to!=pre)
    

        dfs(to,x);

        if(dp[1][to]<=dp[0][to])
        
            flag=true;
            ans+=dp[1][to];
            mn=min(mn,dp[1][to]-dp[0][to]);
        
        else
        
            ans+=dp[0][to];
            mn=min(mn,dp[1][to]-dp[0][to]);
        
    
    if(flag==false)ans+=mn;
    dp[1][x]=ans;

int main()

    int T;
    scanf("%d",&T);
    for(int tt=1;tt<=T;tt++)
    
        int n;
        scanf("%d",&n);
        for(int i=1;i<=n;i++)v[i].clear();

        for(int i=1;i<=n;i++)dp[1][i]=dp[0][i]=0;

        for(int i=1;i<n;i++)
        
            int temp;
            scanf("%d",&temp);
            v[i+1].push_back(temp);
            v[temp].push_back(i+1);
        
        dfs1(1,1);
        dfs(1,1);
        printf("Case #%d: %d\\n",tt,dp[1][1]);
    

    return 0;