LeetCode刷題筆記-009:palindrome number(迴文數)
阿新 • • 發佈:2018-11-09
題目描述:
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?
程式碼如下:
class Solution {
public:
bool isPalindrome(int x) {
int revhalf=0;
int slow=x,fast=x;
//revhalf是將slow即x反轉一半後的值,然後將slow和revhalf比較
if(x<0||(x>0&&x%10==0))return false;//如果最後一位為0也不可能為迴文數
while(fast){
revhalf=revhalf*10+slow%10;
slow/=10;
fast/=100;
}
//如果x是奇位數,則slow等於(revhalf/10),如果slow是偶位數,則slow等於revhalf
return slow==revhalf||slow==(revhalf/10);
}
};