acwing 789 数的范围

#include<iostream>
#include<cstring>
#include<algorithm>
 
using namespace std ;
const int N = 100010 ;
int a[N] ;
int n , q ;
int main(){
 
  cin >> n >> q ;
  for(int i = 0 ; i < n ; i ++) cin >> a[i] ;
  while(q --){
    int k ; cin >> k ;
    int l = 0 , r= n -1;
    while(l < r){
      int mid = (l+r)>>1 ;
      if(a[mid] >= k) r = mid ;
      else l = mid + 1 ;   
    }
    if(a[l] != k) {
      cout << "-1 -1" << endl ;
      continue ;
    }
    else {
      cout << l << " "  ;
      int l2 = 0 , r2 = n-1 ; 
      while(l2 < r2) {
        int mid = l2 + r2 + 1 >> 1 ;
        if(a[mid] <= k) l2 = mid ;
        else r2 = mid - 1 ;
      }
      cout << l2 << endl ;
    }
  }
  return 0 ;
}