题目

Notice that the number 123456789 is a 9-digit number consisting exactly the numbers from 1 to 9, with no duplication. Double it we will obtain 246913578, which happens to be another 9-digit number consisting exactly the numbers from 1 to 9, only in a different permutation. Check to see the result if we double it again!

Now you are suppose to check if there are more numbers with this property. That is, double a given number with k digits, you are to tell if the resulting number consists of only a permutation of the digits in the original number.

Input Specification:

Each input contains one test case. Each case contains one positive integer with no more than 20 digits.

Output Specification:

For each test case, first print in a line “Yes” if doubling the input number gives a number that consists of only a permutation of the digits in the original number, or “No” if not. Then in the next line, print the doubled number.

Sample Input:

1

1234567899

Sample Output:

1
2

Yes
2469135798

题解

思路

• 建立一个哈希表，存放每个字符出现的次数
• 将原数乘以2后，和哈希表每个字符出现的次数作对比
• 完事儿嗷

数据结构

• _dict 是一个哈希表，对每个键默认值是0
  • 键是0到9的字符
  • 值是它出现的次数

算法

• 对作为字符串的原数，按照每一个字符出现的次数添加到哈希表
• 将原数乘以2,对每一个出现的字符，哈希表相应减一
• 如果哈希表不是每一项都为0,那么就说明是No

代码

因为使用Python能AC，因此只放了Python的代码。

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from collections import defaultdict

_dict = defaultdict(int)
a = input()
for i in a:
    _dict[i] += 1
a = str(int(a) * 2)
for i in a:
    _dict[i] -= 1
for i in "0123456789":
    if _dict[i] != 0:
        print("No")
        break
else:
    print("Yes")
print(a)