Submission #1030381

#	Time	Username	Problem	Language	Result	Execution time	Memory
1030381		sleepntsheep	Colors (BOI20_colors)	C11	9 / 100	1 ms	344 KiB

Colors

#include<stdio.h>
#include<stdlib.h>
int a_;
int ask(int c){printf("? %d\n",c);fflush(stdout);scanf("%d",&a_);return a_;}
void report(int C){printf("= %d\n", C);fflush(stdout);exit(0);}
int main(){
    long long n;
    scanf("%lld",&n);
    if(n<=64){
        if(n==1)report(1);
        ask(1);
        if(!ask(n))report(n);
        for(int r=n-1,l=2,d=n-1,i=1,cc=0;cc<n-2;++i,--d,++cc)
            if(i%2&&!ask(l++))report(d);
            else if(i%2==0&&!ask(r--))report(d);
        report(1);
    }
    if(n<=125){
        int m = n / 2 + 1;
        ask(m);
        int mid = ask(1);
        if (!ask(n))report(n);
        if(mid){
            for(int r=m-1,l=2,d=m-1,i=1,cc=0;d>=1;++i,--d,++cc)
                if(i%2&&!ask(l++))report(d);
                else if(i%2==0&&!ask(r--))report(d);
        }else{
            for(int r=n-1,l=2,d=n-1,i=1,cc=0;d>=1;++i,--d,++cc){
                if(i%2){
                    if(l==m)report(1);
                    if(!ask(l++))report(d);
                }
                else if(i%2==0){
                    if(r==m)report(1);
                    else if(!ask(r--)) report(d);
                }
            }
        }
    }
}

Compilation message (stderr)

Colors.c: In function 'ask':
Colors.c:4:50: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
    4 | int ask(int c){printf("? %d\n",c);fflush(stdout);scanf("%d",&a_);return a_;}
      |                                                  ^~~~~~~~~~~~~~~
Colors.c: In function 'main':
Colors.c:8:5: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 |     scanf("%lld",&n);
      |     ^~~~~~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 13
• Subtask 3: 0 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 33