Submission #943051

#	Time	Username	Problem	Language	Result	Execution time	Memory
943051		yeediot	Building 4 (JOI20_building4)	C++14	0 / 100	2 ms	4564 KiB

building4

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define pii pair<int,int>
#define pb push_back
#define sz(x) (int)(x.size())
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define vi vector<int>
#define vp vector<pii>
#define vvi vector<vi>
#define ykh mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count())
#define __lg(x) 63-__builtin_clzll(x)
#define pow2(x) (1LL<<x)
void __print(int x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef local
void setio(){freopen("/Users/iantsai/Library/Mobile Documents/com~apple~CloudDocs/cpp/Empty.md","r",stdin);}
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
void setio(){}
#define debug(x...)
#endif
void setIO(string s) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
}
struct line{
    int a,b;
    int operator()(const int x)const{
        return a*x+b;
    }
};
bool check(line l1,line l2,line l3){
    return (l3.b-l2.b)*(l1.a-l2.a)<=(l2.b-l1.b)*(l2.a-l3.a);
}
const int mxn=5e5+5;
pii dp[mxn][2];
int a[mxn];
int b[mxn];
void upd(pii &a,pii b,bool tf){
    a.F=min(a.F,tf+b.F);
    a.S=max(a.S,tf+b.S);
}
signed main(){
    setio();
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int n;
    cin>>n;
    for(int i=1;i<=2*n;i++){
        cin>>a[i];
    }
    for(int i=1;i<=2*n;i++){
        cin>>b[i];
    }
    for(int i=1;i<=2*n;i++){
        for(int j=0;j<2;j++){
            dp[i][j]={1e18,-1e18};
        }
    }
    for(int i=1;i<=2*n;i++){
        if(a[i-1]<=a[i])upd(dp[i][0],dp[i-1][0],1);
        if(a[i-1]<=b[i])upd(dp[i][1],dp[i-1][0],0);
        if(b[i-1]<=a[i])upd(dp[i][0],dp[i-1][1],1);
        if(b[i-1]<=b[i])upd(dp[i][1],dp[i-1][1],0);
        debug(dp[i][0],dp[i][1]);
    }
    if(dp[2*n][0].F<=n and n<=dp[2*n][0].S){
        vector<char>ans;
        ans.pb('A');
        int cur=n-1;
        int prev=a[n];
        for(int i=2*n;i>=2;i--){
            if(dp[i-1][0].F<=cur and dp[i-1][0].S>=cur and a[i-1]<=prev){
                ans.pb('A');
                cur--;
                prev=a[i-1];
            }
            else{
                ans.pb('B');
                prev=b[i-1];
            }
        }
        reverse(all(ans));
        for(auto i:ans){
            cout<<i;
        }
        cout<<'\n';
    }
    else if(dp[2*n][1].F<=n and n<=dp[2*n][1].S){
        vector<char>ans;
        ans.pb('B');
        int cur=n;
        int prev=b[n];
        for(int i=2*n;i>=2;i--){
            if(dp[i-1][0].F<=cur and dp[i-1][0].S>=cur and a[i-1]<=prev){
                ans.pb('A');
                cur--;
                prev=a[i-1];
            }
            else{
                ans.pb('B');
                prev=b[i-1];
            }
        }
        reverse(all(ans));
        for(auto i:ans){
            cout<<i;
        }
        cout<<'\n';
    }
    else{
        cout<<-1<<'\n';
    }
}
 /*
 input:
 
 */















 

Compilation message (stderr)

building4.cpp: In function 'void setIO(std::string)':
building4.cpp:42:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   42 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
building4.cpp:43:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   43 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 11
• Subtask 2: 0 / 89