A. Nearly Lucky Number

最新推荐文章于 2022-10-20 21:19:59 发布

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最新推荐文章于 2022-10-20 21:19:59 发布

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分类专栏： codeforce 文章标签：水题 c++

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本文介绍了一个简单的算法，用于判断一个数是否为近乎幸运数。根据定义，近乎幸运数是指其幸运数字（4和7）数量本身也是一个幸运数的整数。文章通过示例解释了如何实现这一判断，并分享了在解决问题过程中遇到的一些常见错误。

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这道水题在涛神的帮助下顺利过关，一下是几个泪点

1，英语不过关：In the second sample there are 7 lucky digits, 7 is lucky number, so the answer is "YES".它指的是7位数，digit位数，如果位数是幸运数字则输出，这个没考虑到

2，这个lucky number不一定全都是幸运数字，4444000.7777444都是lucky number，一定要把题目要求看仔细。

3，不管是不是lucky number 在用s统计位数的时候，num都要除以10（详见代码）

Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Unfortunately, not all numbers are lucky. Petya calls a number nearly lucky if the number of lucky digits in it is a lucky number. He wonders whether number n is a nearly lucky number.

Input

The only line contains an integer n (1 ≤ n ≤ 10¹⁸).

Please do not use the %lld specificator to read or write 64-bit numbers in С++. It is preferred to use the cin, cout streams or the %I64d specificator.

Output

Print on the single line "YES" if n is a nearly lucky number. Otherwise, print "NO" (without the quotes).

   Sample test(s) 
 
     input 
   
40047

     output 
   
NO

     input 
   
7747774

     output 
   
YES

     input 
   
1000000000000000000

     output 
   
NO

Note

In the first sample there are 3 lucky digits (first one and last two), so the answer is "NO".

In the second sample there are 7 lucky digits, 7 is lucky number, so the answer is "YES".

In the third sample there are no lucky digits, so the answer is "NO".

#include<iostream>
using namespace std;

int main()
{
    long long  s;
    cin>>s;
    int c=0,i;
    while(s)
    {
    i=s%10;
    if((s%10==7)||(s%10==4))  c++;
    s=s/10;//这句别写在if 语句里面
    }
    if(c==7||c==4) cout<<"YES"<<endl;
    else cout<<"NO"<<endl;
    return 0;

}