LeetCode-Strobogrammatic Number

LiBlog發表於2016-08-23
LeetCode

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

Solution:

 1 public class Solution {
 2     public boolean isStrobogrammatic(String num) {
 3         int p1 = 0, p2 = num.length() - 1;
 4         while (p1 <= p2) {
 5             if (!isValidPair(num.charAt(p1), num.charAt(p2)))
 6                 return false;
 7             p1++;
 8             p2--;
 9         }
10         return true;
11     }
12 
13     public boolean isValidNum(int num) {
14         if (num == 0 || num == 1 || num == 6 || num == 8 || num == 9)
15             return true;
16 
17         return false;
18     }
19 
20     public boolean isValidPair(char c1, char c2) {
21         int num1 = c1 - '0';
22         int num2 = c2 - '0';
23         if (!isValidNum(num1) || !isValidNum(num2))
24             return false;
25 
26         if ((num1 == 6 && num2 != 9) || (num1 == 9 && num2 != 6)) {
27             return false;
28         } else if (num1 + num2 != 15 && num1 != num2) {
29             return false;
30         }
31         return true;
32     }
33 }

 

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