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ReverseInteger.java
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50 lines (46 loc) · 1.46 KB
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package algorithm.lc;
/**
* Reverse digits of an integer.
*
* Example1: x = 123, return 321 Example2: x = -123, return -321
*
* Have you thought about this? Here are some good questions to ask before
* coding. Bonus points for you if you have already thought through this!
*
* If the integer's last digit is 0, what should the output be? ie, cases such
* as 10, 100.
*
* Did you notice that the reversed integer might overflow? Assume the input is
* a 32-bit integer, then the reverse of 1000000003 overflows. How should you
* handle such cases?
*
* Throw an exception? Good, but what if throwing an exception is not an option?
* You would then have to re-design the function (ie, add an extra parameter).
*
*/
// O(n) space, O(n) time, where n is the length of digit.
public class ReverseInteger {
public class Solution {
public int reverse(int x) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if (x == Integer.MIN_VALUE) {
return 0;
}
int res = 0;
int sign = x > 0? 1 : -1;
x = Math.abs(x);
while (x > 0) {
int digit = x % 10;
if (sign == 1 && (Integer.MAX_VALUE - digit) / 10 < res) {
return 0; // overflow
}
else if (sign == -1 && (Integer.MIN_VALUE + digit) / 10 > res) {
return 0; // underflow
}
x /= 10;
res = res * 10 + sign * digit;
}
return res;
}
}
}