Submission #1111632

#	Time	Username	Problem	Language	Result	Execution time	Memory
1111632		onlk97	Building 4 (JOI20_building4)	C++14	100 / 100	199 ms	45648 KiB

building4

#include <bits/stdc++.h>
#define x first
#define y second
#define pb push_back
using namespace std;
using pii=pair <int,int>;
pii merge(pii a,pii b){
    if (a.x==-1) return b;
    if (b.x==-1) return a;
    return {min(a.x,b.x),max(a.y,b.y)};
}
int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int n;
    cin>>n;
    int a[2][2*n+1];
    for (int i=0; i<2; i++){
        for (int j=1; j<=2*n; j++) cin>>a[i][j];
    }
    pii dp[2][2*n+1];
    for (int i=0; i<2; i++){
        for (int j=1; j<=2*n; j++) dp[i][j]={-1,-1};
    }
    dp[0][1]={0,0}; dp[1][1]={1,1};
    for (int j=2; j<=2*n; j++){
        for (int i=0; i<2; i++){
            for (int k=0; k<2; k++){
                if (a[k][j-1]<=a[i][j]){
                    if (dp[k][j-1].x!=-1) dp[i][j]=merge(dp[i][j],{dp[k][j-1].x+i,dp[k][j-1].y+i});
                }
            }
        }
    }
    int lst=-1;
    if (dp[0][2*n].x<=n&&n<=dp[0][2*n].y) lst=0;
    if (dp[1][2*n].x<=n&&n<=dp[1][2*n].y) lst=1;
    if (lst==-1) {
        cout<<"-1\n";
        return 0;
    }
    string ans="";
    int bal=n;
    for (int i=2*n; i>0; i--){
        if (!lst) ans+='A';
        else {
            ans+='B';
            bal--;
        }
        if (i==1) break; 
        if (!bal||dp[0][i-1].x<=bal&&bal<=dp[0][i-1].y&&a[0][i-1]<=a[ans.back()-'A'][i]) lst=0;
        else lst=1;
    }
    reverse(ans.begin(),ans.end());
    cout<<ans<<'\n';
}

Compilation message (stderr)

building4.cpp: In function 'int main()':
building4.cpp:50:55: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   50 |         if (!bal||dp[0][i-1].x<=bal&&bal<=dp[0][i-1].y&&a[0][i-1]<=a[ans.back()-'A'][i]) lst=0;
      |                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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