Submission #1022741

#	Time	Username	Problem	Language	Result	Execution time	Memory
1022741		guagua0407	Tug of War (BOI15_tug)	C++17	100 / 100	966 ms	6160 KiB

tug

//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,int>
#define f first
#define s second
#define all(x) x.begin(),x.end()
#define _ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);

int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};

void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}

const int mxn=6e4+5;
int l[mxn],r[mxn],S[mxn];
bool vis[mxn];
bool usedl[mxn],usedr[mxn];

int main() {_
    int n,k;
    cin>>n>>k;
    vector<vector<int>> ls(n),rs(n);
    int all=0;
    for(int i=0;i<2*n;i++){
        cin>>l[i]>>r[i]>>S[i];
        all+=S[i];
        l[i]--;
        r[i]--;
        ls[l[i]].push_back(i);
        rs[r[i]].push_back(i);
    }
    for(int i=0;i<n;i++){
        if(ls[i].empty() or rs[i].empty()){
            cout<<"NO"<<'\n';
            return 0;
        }
    }
    int ans=0;
    for(int i=0;i<2*n;i++){
        if(vis[i]) continue;
        int state=-1;
        {
            int cnt=0;
            for(auto v:ls[l[i]]){
                if(!vis[v]) cnt++;
            }
            if(cnt==1){
                state=0;
            }
        }
        {
            int cnt=0;
            for(auto v:rs[r[i]]){
                if(!vis[v]) cnt++;
            }
            if(cnt==1){
                state=1;
            }
        }
        if(state==-1) continue;
        int x=i;
        while(x!=-1){
            vis[x]=true;
            int cnt=0;
            int nxt;
            if(state==0){
                usedl[l[x]]=true;
                state=1;
                ans+=S[x];
                for(auto v:rs[r[x]]){
                    if(!vis[v]){
                        cnt++;
                        nxt=v;
                    }
                }
                if(cnt==1) x=nxt;
                else x=-1;
            }
            else{
                usedr[r[x]]=true;
                state=0;
                for(auto v:ls[l[x]]){
                    if(!vis[v]){
                        cnt++;
                        nxt=v;
                    }
                }
                if(cnt==1) x=nxt;
                else x=-1;
            }
        }
    }
    for(int i=0;i<n;i++){
        {
            int cnt=0;
            for(auto v:ls[i]){
                if(!vis[v]) cnt++;
            }
            if(!usedl[i] and cnt!=2){
                cout<<"NO"<<'\n';
                return 0;
            }
        }
        {
            int cnt=0;
            for(auto v:rs[i]){
                if(!vis[v]) cnt++;
            }
            if(!usedr[i] and cnt!=2){
                cout<<"NO"<<'\n';
                return 0;
            }
        }
    }
    vector<int> cand;
    for(int i=0;i<2*n;i++){
        if(vis[i]) continue;
        int x=i;
        int a=0;
        int b=0;
        int state=0;
        while(x!=-1){
            vis[x]=true;
            if(state==0){
                state=1;
                a+=S[x];
                bool tf=false;
                for(auto v:ls[l[x]]){
                    if(!vis[v]){
                        x=v;
                        tf=true;
                        break;
                    }
                }
                if(!tf) x=-1;
            }
            else{
                state=0;
                b+=S[x];
                bool tf=false;
                for(auto v:rs[r[x]]){
                    if(!vis[v]){
                        x=v;
                        tf=true;
                        break;
                    }
                }
                if(!tf) x=-1;
            }
        }
        ans+=a;
        cand.push_back(b-a);
    }
    bitset<mxn*20> b;
    b[ans]=1;
    for(auto v:cand){
        if(v>=0) b|=(b<<v);
        else b|=(b>>(-v));
    }
    int cur=all/2;
    while((all-cur)-cur<=k){
        if(b[cur] or b[all-cur]){
            cout<<"YES"<<'\n';
            return 0;
        }
        cur--;
    }
    cout<<"NO"<<'\n';
    return 0;
}
//maybe its multiset not set
//yeeorz
//laborz

Compilation message (stderr)

tug.cpp: In function 'void setIO(std::string)':
tug.cpp:15:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   15 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tug.cpp:16:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tug.cpp: In function 'int main()':
tug.cpp:68:19: warning: 'nxt' may be used uninitialized in this function [-Wmaybe-uninitialized]
   68 |             vis[x]=true;
      |             ~~~~~~^~~~~

• Subtask 1: 18 / 18
• Subtask 2: 30 / 30
• Subtask 3: 23 / 23
• Subtask 4: 29 / 29