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。

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <iostream>

 4 using namespace std;

 5 const int MAX_SIZE = 5E5 + 10;

 6 int num[MAX_SIZE];

 7 int a[MAX_SIZE];

 8 

 9 void quick_sort(int s[], int l, int r)

10 {

11     if(l < r)

12     {

13         int i = l, j = r, x = s[l];

14         while(i < j)

15         {

16             while(i < j && s[j] >= x)

17                 j--;

18             if(i < j)

19                 s[i++] = s[j];

20 

21             while(i < j && s[i] < x)

22                 i++;

23             if(i < j)

24                 s[j--] = s[i];

25         }

26         s[i] = x;

27         quick_sort(s, l, i-1);

28         quick_sort(s, i+1, r);

29     }

30 }

31 

32 ///二分查下届

33 int BSearchLowerBound(int arry[], int low, int high, int target)

34 {

35     if(high < low || target <= arry[low])

36         return -1;

37     int mid = (low + high + 1) / 2;

38     while(low < high)

39     {

40         if(arry[mid] < target)

41             low = mid;

42         else

43             high = mid - 1;

44         mid = (low + high + 1)/2;

45     }

46     return mid;

47 }

48 

49 int BSearchLowerBound_1(int arry[], int low, int high, int target)

50 {

51     if(high < low || target < arry[low])

52         return -1;

53     int mid = (low + high + 1) / 2;

54     while(low < high)

55     {

56         if(arry[mid] <= target)

57             low = mid;

58         else

59             high = mid - 1;

60         mid = (low + high + 1)/2;

61     }

62     return mid;

63 }

64 

65 int main()

66 {

67     int n, m;

68     int x, y, ans;

69     while(~scanf("%d %d", &n, &m))

70     {

71         for(int i = 0; i < n; i++)

72         {

73             scanf("%d", num+i);

74         }

75         //quick_sort 下标从 0 开始

76         quick_sort(num, 0, n-1);

77 

78         for(int i = 0; i < m; i ++)

79         {

80             scanf("%d %d", &x, &y);

81 

82             ans = BSearchLowerBound_1(num, 0, n-1, y) - BSearchLowerBound(num, 0, n-1, x);

83 

84             printf("%d\n", ans);

85         }

86     }

87     return 0;

88 }

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