Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
Example 1:
Input: 121 Output: true
Example 2:
Input: -121 Output: false Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
Example 3:
Input: 10 Output: false Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
Follow up:
Coud you solve it without converting the integer to a string?
题意:
判断是否为回文数
Solution1: reverse the original number as reversedInt, if reversedInt == original number, it is a Palindrome
original number reversedInt isPalindrome()
123 321 flase
121 121 true
code
1 /* 2 Time Complexity: O(n), loop each digit of input number 3 Space Complexity: O(1), allocate a variable temp 4 */ 5 class Solution { 6 public boolean isPalindrome(int x) { 7 // handle input is negative like -121 or end with 0 8 if (x < 0 || (x != 0 && x % 10 == 0)) return false; 9 10 int temp = x; 11 long sum = 0; 12 while (x != 0) { 13 sum = sum * 10 + x % 10; 14 x = x / 10; 15 } 16 return (int)sum == temp; 17 } 18 }
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