246. Strobogrammatic Number
https://www.lintcode.com/problem/strobogrammatic-number/description
https://leetcode.com/problems/strobogrammatic-number
247-strobogrammatic-number-ii
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https://leetcode.com/problems/strobogrammatic-number
A mirror number is a number that looks the same when rotated 180 degrees (looked at upside down).For example, the numbers "69", "88", and "818" are all mirror numbers.
Write a function to determine if a number is mirror. The number is represented as a string.
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Related problems247-strobogrammatic-number-ii
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| public class Solution { | |
| /** | |
| * @param num: a string | |
| * @return: true if a number is strobogrammatic or false | |
| */ | |
| public boolean isStrobogrammatic(String num) { | |
| Map<Character, Character> reverse = new HashMap<Character, Character>(); | |
| reverse.put('6', '9'); | |
| reverse.put('9', '6'); | |
| reverse.put('0', '0'); | |
| reverse.put('1', '1'); | |
| reverse.put('8', '8'); | |
| Set<Character> invalid = new HashSet<Character>(); | |
| invalid.add('2'); | |
| invalid.add('3'); | |
| invalid.add('4'); | |
| invalid.add('5'); | |
| invalid.add('7'); | |
| int i = 0, j = num.length() - 1; | |
| while (i <= j) { | |
| char first = num.charAt(i); | |
| char second = num.charAt(j); | |
| if (invalid.contains(first) || invalid.contains(second)) { | |
| return false; | |
| } | |
| if (reverse.containsKey(first) && reverse.get(first) != second) { | |
| return false; | |
| } | |
| i++; | |
| j--; | |
| } | |
| return true; | |
| } | |
| } |
