1056. Confusing Number
Math ·Problem Statement
link: LeetCode.cn LeetCode
A confusing number is a number that when rotated 180 degrees becomes a different number with each digit valid.
We can rotate digits of a number by 180 degrees to form new digits.
When 0, 1, 6, 8, and 9 are rotated 180 degrees, they become 0, 1, 9, 8, and 6 respectively. When 2, 3, 4, 5, and 7 are rotated 180 degrees, they become invalid. Note that after rotating a number, we can ignore leading zeros.
For example, after rotating 8000, we have 0008 which is considered as just 8. Given an integer n, return true if it is a confusing number, or false otherwise.
Example:
Input: n = 6
Output: true
Input: n = 89
Output: true
Input: n = 1
Output: flase
Solution Approach
Algorithm
Implement
class Solution {
public boolean confusingNumber(int n) {
HashMap<Integer, Integer> rotationMap = new HashMap<>();
rotationMap.put(0, 0);
rotationMap.put(1, 1);
rotationMap.put(6, 9);
rotationMap.put(8, 8);
rotationMap.put(9, 6);
int after = 0;
int origin = n;
while (n != 0) {
int num = n % 10;
if (!rotationMap.containsKey(num)) {
return false;
}
num = rotationMap.get(num);
after = after * 10 + num;
n /= 10;
}
if (origin == after) {
return false;
}
return true;
}
}