LeetCode 246: Strobogrammatic Number
LeetCode 246 Solution Explanation
Explanation
To solve this problem, we need to determine whether a given number is a strobogrammatic number. A strobogrammatic number is a number that looks the same when rotated 180 degrees.
We can create a mapping of valid strobogrammatic pairs: (0,0), (1,1), (6,9), (8,8), (9,6).
We iterate through the number from the start and end simultaneously, checking if the pair of digits at each position is a valid strobogrammatic pair. If they are not, we return false. If all pairs are valid, we return true.
Time complexity: O(N) where N is the number of digits in the input number. Space complexity: O(1)
LeetCode 246 Solutions in Java, C++, Python
class Solution {
public boolean isStrobogrammatic(String num) {
int left = 0, right = num.length()-1;
while (left <= right) {
if (!isValid(num.charAt(left), num.charAt(right))) {
return false;
}
left++;
right--;
}
return true;
}
private boolean isValid(char c1, char c2) {
return (c1 == '0' && c2 == '0') || (c1 == '1' && c2 == '1') || (c1 == '6' && c2 == '9') || (c1 == '8' && c2 == '8') || (c1 == '9' && c2 == '6');
}
}Interactive Code Editor for LeetCode 246
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