https://www.luogu.org/problem/show?pid=CF1029C

1 #include
     
       2 using namespace std ; 3 #define LL long long  4  5 LL read(){ 6     char c ; 7     int sign = 1 ; 8     while((c = getchar()) > '9' || c < '0') 9         if(c == '-') sign = -1 ;10     LL ans = c - '0' ;11     while((c = getchar()) <='9' && c >= '0')12         ans = ans * 10 + c - '0' ;13     return ans * sign ;14 }15 16 int n ;17 LL l[400000] , r[400000] ;18 LL la = 0 , ra = 10e9 + 1 ;19 20 void answer(){21     la = 0 , ra = 10e9 + 1 ;22     for(int i = 1 ; i <= n ; ++ i){23         la = max(la , l[i]) ;24         ra = min(ra , r[i]) ;25     }26 }27 28 int main(){29     n = read() ;30     LL ansl = 0 , ansr = 0 ;31     r[0] = 10e9 + 1 ;32     l[0] = 0 ;33     for(int i = 1 ; i <= n ; ++ i){34         l[i] = read() , r[i] = read() ;35     }36     answer() ;37     if(la > ra) {38         printf("%d",0);39         return 0 ;40     }41     for(int i = 1 ; i <= n ; ++ i){42         if(l[i] == la){43             if(r[i] < r[ansl]) {44                 ansl = i ;45             }46         }47         if(r[i] == ra){48             if(l[i] > l[ansr]){49                 ansr = i ;50             }51         }52     }53     if(ansr == ansl){54         l[ansr] = 0 ;55         r[ansr] = 10e9 + 1 ;56         answer() ;57         printf("%ld",ra - la) ;58         return 0 ;59     }60     else {61         LL ii = l[ansr] ;62         LL ff = r[ansr] ;63         l[ansr] = 0 , r[ansr] = 10e9 + 1 ;64         answer() ;65         LL len = ra - la ;66         l[ansr] = ii , r[ansr] = ff ;67         l[ansl] = 0 , r[ansl] = 10e9 + 1 ; 68         answer() ;69         len = max(len , ra - la) ;70         printf("%ld",len) ;71         return 0 ;72     }73 }