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PalindromeNumber.cpp
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PalindromeNumber.cpp
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// Source: https://leetcode.com/problems/palindrome-number/
// 2015/4/8
/**********************************************************************************************
// My Solution
class Solution {
public:
bool isPalindrome(int x) {
if (x < 0 || x > INT_MAX) return false;
if (x < 10) return true;
string str = to_string(x);
bool ret = true;
for (int i = 0, j = str.size() - 1;
i < j; ++i, --j) {
if (str[i] != str[j]) {
ret = false;
break;
}
}
return ret;
}
}; // 158ms
// Reference the solution of haoel
// (https://github.com/haoel/leetcode/blob/master/algorithms/palindromeNumber/palindromeNumber.cpp)
// Thanks!
// Note: How he get the reversed integer
class Solution {
public:
bool isPalindrome(int x) {
return (x >= 0 && x == reverse(x));
}
private:
int reverse(int x) {
int ret = 0;
while (x) {
ret = ret * 10 + x % 10;
x /= 10;
}
return ret;
}
}; // 131ms
*******************************************************************************************************/
// Note: How he obtained the pair of digits
class Solution {
public:
bool isPalindrome(int x) {
// x is a negative
if (x < 0) return false;
// the order of magnitudes of the integer
int len = 1;
for (; x/len >= 10; len *= 10);
while (x) {
int left = x/len;
int right = x % 10;
if (left != right) return false;
x = (x % len) / 10;
len /= 100;
}
return true;
}
}; // 123ms