[LeetCode] Palindrome Number

劉厚水發(fā)布于2019-08-14 14:03 / 2742人閱讀

摘要：逐位看官，這兩種解法一看便知，小子便不多費(fèi)唇舌了。字符數(shù)組比較法原數(shù)翻轉(zhuǎn)比較法

Problem

Determine whether an integer is a palindrome. Do this without extra space.

click to show spoilers.

Some hints:
Could negative integers be palindromes? (ie, -1)
NO

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

Note

逐位看官，這兩種解法一看便知，小子便不多費(fèi)唇舌了。

Solution 字符數(shù)組比較法

public class Solution {
    public boolean isPalindrome(int x) {
        if (x >= Integer.MAX_VALUE || x < 0) return false;
        int digit = 0, x2 = x;
        while (x2 != 0) {
            x2 /= 10;
            digit++;
        }
        int[] A = new int[digit];
        while (x != 0) {
            A[--digit] = x % 10;
            x /= 10;
        }
        int left = 0, right = A.length-1;
        while (left < right) {
            if (A[left++] != A[right--]) return false;
        }
        return true;
    }
}

原數(shù)翻轉(zhuǎn)比較法

public class Solution {
    public boolean isPalindrome(int x) {
        if (x < 0) return false;
        long rvs = 0;
        int i = 0, org = x;
        while (x != 0) {
            i = x % 10;
            rvs = rvs * 10 + i;
            x /= 10;
        }
        return rvs == org;
    }
}

云服務(wù)器 GPU云服務(wù)器 palindrome LeetCode LeetCode_String leetcode_35_SearchIn

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