清华学堂 Range

Descriptioin

Let S be a set of n integral points on the x-axis. For each given interval [a, b], you are asked to count the points lying inside.

Input

The first line contains two integers: n (size of S) and m (the number of queries).

The second line enumerates all the n points in S.

Each of the following m lines consists of two integers a and b and defines an query interval [a, b].

Output

The number of points in S lying inside each of the m query intervals.

Example

Input

5 2
1 3 7 9 11
4 6
7 12

Output

0
3

Restrictions

0 <= n, m <= 5 * 10^5

For each query interval [a, b], it is guaranteed that a <= b.

Points in S are distinct from each other.

Coordinates of each point as well as the query interval boundaries a and b are non-negative integers not greater than 10^7.

Time: 2 sec

Memory: 256 MB

这道题目，好早以前就接触过，那时候数据结构刚学，什么也不懂，今年又来刷这套题了，感觉还好

题目求 [a, b] 内所有的元素个数，二分搜索，求下界，对a求它严格的下界， 对b求它不严格的下界，搞定。

这道题目不用二分，只能拿一部分分数。

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 using namespace std;
 const int MAX_SIZE = 5E5 + ;
 int num[MAX_SIZE];
 int a[MAX_SIZE];

 void quick_sort(int s[], int l, int r)
 {
     if(l < r)
     {
         int i = l, j = r, x = s[l];
         while(i < j)
         {
             while(i < j && s[j] >= x)
                 j--;
             if(i < j)
                 s[i++] = s[j];

             while(i < j && s[i] < x)
                 i++;
             if(i < j)
                 s[j--] = s[i];
         }
         s[i] = x;
         quick_sort(s, l, i-);
         quick_sort(s, i+, r);
     }
 }

 ///二分查下届
 int BSearchLowerBound(int arry[], int low, int high, int target)
 {
     if(high < low || target <= arry[low])
         return -;
     int mid = (low + high + ) / ;
     while(low < high)
     {
         if(arry[mid] < target)
             low = mid;
         else
             high = mid - ;
         mid = (low + high + )/;
     }
     return mid;
 }

 int BSearchLowerBound_1(int arry[], int low, int high, int target)
 {
     if(high < low || target < arry[low])
         return -;
     int mid = (low + high + ) / ;
     while(low < high)
     {
         if(arry[mid] <= target)
             low = mid;
         else
             high = mid - ;
         mid = (low + high + )/;
     }
     return mid;
 }

 int main()
 {
     int n, m;
     int x, y, ans;
     while(~scanf("%d %d", &n, &m))
     {
         for(int i = ; i < n; i++)
         {
             scanf("%d", num+i);
         }
         //quick_sort 下标从 0 开始
         quick_sort(num, , n-);

         for(int i = ; i < m; i ++)
         {
             scanf("%d %d", &x, &y);

             ans = BSearchLowerBound_1(num, , n-, y) - BSearchLowerBound(num, , n-, x);

             printf("%d\n", ans);
         }
     }
     return ;
 }