PAT-A-1085 Perfect Sequence 【二分查找】

Given a sequence of positive integers and another positive integer p. The sequence is said to be a perfect sequence if M≤m×p where M and m are the maximum and minimum numbers in the sequence, respectively.

Now given a sequence and a parameter p, you are supposed to find from the sequence as many numbers as possible to form a perfect subsequence.

Input Specification:

Each input file contains one test case. For each case, the first line contains two positive integers N and p, where N (≤10​5​​) is the number of integers in the sequence, and p (≤10​9​​) is the parameter. In the second line there are N positive integers, each is no greater than 10​9​​.

Output Specification:

For each test case, print in one line the maximum number of integers that can be chosen to form a perfect subsequence.

Sample Input:

10 8
2 3 20 4 5 1 6 7 8 9

Sample Output:

8

---

这道题使用upper_bound简直绝了。原因如下：

• upper_load（）返回的是第一个大于所求值得下标，直接减去数组头就是序列的长度
• 内部使用二分查找，速度绝对杠杠的

最后一个用例点没有过，因为没有考虑过int溢出的问题，其实一看到题目中指定了数据的范围是1e9，就应该知道这里有猫腻。

使用long long 保存乘积

#include 
#include 
#include 
#include 
using namespace std;
int main(){
	int a,b;
	scanf("%d %d",&a,&b);
	int temp;
	vector data;
	for(int i=0;ilen-j?max:len-j;
	}
	printf("%d",max);
	return 0;
}