LeetCode: Confusing Number

Confusing Number

Similar Problems:

• CheatSheet: Leetcode For Code Interview
• CheatSheet: Common Code Problems & Follow-ups
• Tag: #hashmap, #rotatelist

Given a number N, return true if and only if it is a confusing number, which satisfies the following condition:

We can rotate digits by 180 degrees to form new digits. When 0, 1, 6, 8, 9 are rotated 180 degrees, they become 0, 1, 9, 8, 6 respectively. When 2, 3, 4, 5 and 7 are rotated 180 degrees, they become invalid. A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.

Example 1:

Input: 6
Output: true
Explanation: 
We get 9 after rotating 6, 9 is a valid number and 9!=6.

Example 2:

Input: 89
Output: true
Explanation: 
We get 68 after rotating 89, 86 is a valid number and 86!=89.

Example 3:

Input: 11
Output: false
Explanation: 
We get 11 after rotating 11, 11 is a valid number but the value remains the same, thus 11 is not a confusing number.

Example 4:

Input: 25
Output: false
Explanation: 
We get an invalid number after rotating 25.

Note:

1. 0 <= N <= 10^9
2. After the rotation we can ignore leading zeros, for example if after rotation we have 0008 then this number is considered as just 8.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

• Solution:

// https://code.dennyzhang.com/confusing-number
// Basic Ideas: hashmap
// Complexity: Time O(1), Space O(1)
func confusingNumber(N int) bool {
    m := map[int]int{0:0, 1:1, 6:9, 8:8, 9:6}
    l1, l2 := []int{}, []int{}
    for N != 0 {
        v := N%10
        _, ok := m[v]
        if !ok { return false }
        l1, l2 = append(l1, v), append(l2, m[v])
        N = N/10
    }

    for i, _ := range l1 {
        if l1[i] != l2[len(l1)-1-i] {
            return true
        }
    }
    return false
}