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?
翻譯
判斷一個整數是否是迴文數。迴文數是指正序(從左向右)和倒序(從右向左)讀都是一樣的整數。
示例 1:
輸入: 121
輸出: true
示例 2:
輸入: -121
輸出: false
解釋: 從左向右讀, 爲 -121 。 從右向左讀, 爲 121- 。因此它不是一個迴文數。
示例 3:
輸入: 10
輸出: false
解釋: 從右向左讀, 爲 01 。因此它不是一個迴文數。
進階:
你能不將整數轉爲字符串來解決這個問題嗎?
分析
轉化爲字符串,倒置字符串若與原來相同,返回true。
c++實現
class Solution {
public:
string reverse(string s) {
for (int i = 0; i <= (s.length()-1)/2; i++)
{
char tmp = s[i];
s[i] = s[s.length()-1-i];
s[s.length()-1-i] = tmp;
}
return s;
}
bool isPalindrome(int x) {
stringstream ss;
ss << x;
string s = ss.str();
string S = reverse(s);
for (int i = 0; i < S.length(); i++)
{
if (S[i] != s[i])
return false;
}
return true;
}
};