Submission #604718

#	Time	Username	Problem	Language	Result	Execution time	Memory
604718		krit3379	The Xana coup (BOI21_xanadu)	C++17	100 / 100	99 ms	23436 KiB

xanadu

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define N 100005

long long st[N],dp[2][2][N],ans;
// good/bad  not pass/pass
vector<int> gr[N];

void upd(long long &x,long long &v0,long long &v1,long long &s,long long &m){
    x+=min(v0,v1);
    s^=v0<=v1?0:1;
    m=min(m,abs(v0-v1));
}

void dfs(int s,int f){
    long long b=0,g=0,sb=0,sg=0,mb=1e9,mg=1e9;
    for(auto x:gr[s]){
        if(x==f)continue;
        dfs(x,s);
        upd(b,dp[1][0][x],dp[1][1][x],sb,mb);
        upd(g,dp[0][0][x],dp[0][1][x],sg,mg);
    }
    dp[sg^st[s]][0][s]=min(g,dp[sg^st[s]][0][s]);
    dp[sg^st[s]^1][0][s]=min(g+mg,dp[sg^st[s]^1][0][s]);
    dp[sb^st[s]^1][1][s]=min(b+1,dp[sb^st[s]^1][1][s]);
    dp[sb^st[s]][1][s]=min(b+mb+1,dp[sb^st[s]][1][s]);
}

int main(){
    int n,i,j,k,a,b;
    scanf("%d",&n);
    for(i=1;i<n;i++){
        scanf("%d %d",&a,&b);
        gr[a].push_back(b);
        gr[b].push_back(a);
    }
    for(i=0;i<2;i++)for(j=0;j<2;j++)for(k=1;k<=n;k++)dp[i][j][k]=1e9;
    for(i=1;i<=n;i++)scanf("%lld",&st[i]);
    dfs(1,0);
    if(min(dp[0][0][1],dp[0][1][1])<1e9)printf("%lld",min(dp[0][0][1],dp[0][1][1]));
    else printf("impossible");
    return 0;
}

Compilation message (stderr)

xanadu.cpp: In function 'int main()':
xanadu.cpp:33:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
xanadu.cpp:35:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |         scanf("%d %d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~~
xanadu.cpp:40:27: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   40 |     for(i=1;i<=n;i++)scanf("%lld",&st[i]);
      |                      ~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30