leetcode-9-Palindrome-Number

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描述

Given an integer x, return true if x is palindrome integer.

An integer is a palindrome when it reads the same backward as forward. For example, 121 is palindrome while 123 is not.

Example 1:

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Input: x = 121
Output: true

Example 2:

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Input: x = -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:

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Input: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.

Example 4:

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Input: x = -101
Output: false

Constraints:

  • -231 <= x <= 231 - 1

Follow up: Could you solve it without converting the integer to a string?

分析

简单题。

解决方案1（Python）

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class Solution:
    def isPalindrome(self, x: int) -> bool:
        return str(x)== str(x)[::-1]

解决方案2(C++)

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class Solution {
public:
    bool isPalindrome(int x) {
        if(x < 0) {
            return false;
        }
        if(x == 0) {
            return true;
        }
        int base = 1;
        while(x / base >= 10) {
            base *= 10;
        }
        
        while(x) {
            int left = x / base;
            int right = x % 10;
            if(left != right){
                return false;
            }
            x -= base*left;
            base /= 100;
            x /= 10;
        }
        return true;
    }
};

解决方案3（Golang）

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func isPalindrome(x int) bool {
    if x < 0 {
        return false
    }
    nums := []int {}
    for x != 0 {
        nums = append(nums, x%10)
        x /= 10
    }
    length := len(nums)
    for i := 0; i < length/2; i++ {
        if nums[i] != nums[length-i-1] {
            return false
        }
    }
    return true
}

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