leetcode 9. Palindrome Number
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?
First try, convert integer to string.
class Solution {
public boolean isPalindrome(int x) {
String a = String.valueOf(x);
return a.equals(reverse(a));
}
public String reverse(String str){
int len = str.length();
String re = "";
for(int i = 0; i< len; i++){
re = str.substring(i,i+1) + re;
}
return re;
}
}
Second try without converting the integer to string.
class Solution {
public boolean isPalindrome(int x) {
if(x < 0){
return false;
}
return x == reverse(x);
}
public Integer reverse(int x){
int result = 0;
while(x != 0){
result = result * 10 + x % 10;
x = x/10;
}
return result;
}
}
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