NOIP模拟测试21「折纸·不等式」

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define A 3100000
ll cj[A],questions[A];
ll len,l,r,n,QAQ;
int main(){
    scanf("%lld%lld",&len,&QAQ);
    l=0,r=len;
    for(ll i=1,a;i<=QAQ;i++){
        scanf("%lld",&questions[i]);
    }
    for(ll i=1;i<=QAQ;i++){

        ll llen=questions[i]-l;
        ll rlen=r-questions[i];
//        printf("ques=%lld llen=%lld rlen=%lld\n",questions[i],l,r);
        if(llen==0||rlen==0) continue;
        if(llen<rlen){    
            l=questions[i];        
            for(ll j=i+1;j<=QAQ;j++){
                if(questions[j]<questions[i])    
                questions[j]=questions[i]+abs(questions[j]-questions[i]);
            }
            
        }
        if(llen>=rlen){
            r=questions[i];
            for(ll j=i+1;j<=QAQ;j++){
                if(questions[j]>questions[i])
                questions[j]=questions[i]-abs(questions[j]-questions[i]);
            }
        }
    }
    printf("%lld\n",r-l);
}