9. Palindrome Number

LeetCode
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My Solution (String Builder and compare)

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class Solution {
    public boolean isPalindrome(int x) {
        // convert to string
        String str = String.valueOf(x);
        // new string builder
        StringBuilder sb = new StringBuilder();
        // save from tight to left
        for (int pos = str.length() - 1; pos >= 0; pos--) {
            sb.append(str.charAt(pos));
        }
        // compare strings
        return str.equals(sb.toString());
    }
}

Math

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class Solution {
    public boolean isPalindrome(int x) {
        // negative & end with `0`
        if (x < 0 || (x % 10 == 0 && x != 0)) return false;

        int reverted = 0;
        while (x > reverted) {
            reverted = reverted * 10 + x % 10;
            x /= 10;
        }

        // caompare first half and last half
        return x == reverted || x == reverted / 10;
    }
}

Remarks:

  1. Use reverted/10 to ignore the middle number (if odd)