【朱迪的LeetCode刷题笔记】9. Palindrome Number #Easy #C

Judie

1. 
   
2. 9. Palindrome Number #Easy
   
3. 
   
4. Given an integer x, return true if x is palindrome integer.
   
5. 
   
6. An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.
   
7. 
   
8. 
   
9. Example 1:
   
10. 
    
11. Input: x = 121
    
12. Output: true
    
13. 
    
14. Example 2:
    
15. 
    
16. Input: x = -121
    
17. Output: false
    
18. Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
    
19. 
    
20. Example 3:
    
21. 
    
22. Input: x = 10
    
23. Output: false
    
24. Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
    
25. 
    
26. Example 4:
    
27. 
    
28. Input: x = -101
    
29. Output: false
    
30. 
    
31. 
    
32. Constraints:
    
33. 
    
34. -231 <= x <= 231 - 1
    
35. 
    
36. 
    
37. Follow up: Could you solve it without converting the integer to a string?
    

复制代码

C

1. 
   
2. #include <limits.h>
   
3. 
   
4. bool isPalindrome(int x){
   
5.     if (x < 0) {
   
6.         return false;
   
7.     }
   
8.     if (x == 0) {
   
9.         return true;
   
10.     }
    
11.     int temp_x = x;
    
12.     int reverse_x = 0;
    
13.     while (temp_x) {
    
14.         if (reverse_x > (INT_MAX - (temp_x % 10)) / 10) {
    
15.             return x / 10 == reverse_x && x % 10 == temp_x;
    
16.         }
    
17.         reverse_x = (reverse_x * 10) + (temp_x % 10);
    
18.         temp_x = temp_x / 10;
    
19.     }
    
20.     return reverse_x == x;
    
21. }
    

复制代码