Reverse Integer Problem LeetCode (Reverse digits of an integer)

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

SPOILERS:

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?

For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

This problem is popular in LeetCode, GeeksForGeeks, GeeksForGeeks Forum, and StackOverFlow A collection of hundreds of interview questions and solutions are available in our blog at Interview Question Solutions

SOLUTION:
source code: Java

	import java.text.DateFormat;
	import java.text.SimpleDateFormat;
	import java.util.ArrayList;
	import java.util.Date;
	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	/**
	* Reverse digits of an integer.
	*
	* Example1: x = 123, return 321 Example2: x = -123, return -321
	*
	* click to show spoilers.
	*
	* 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?
	*
	* For the purpose of this problem, assume that your function returns 0 when the
	* reversed integer overflows.
	*
	* Update (2014-11-10): Test cases had been added to test the overflow behavior.
	*/
	/**
	*
	* @author rbaral
	*
	*/
	public class ReverseInteger {
	public static void main(String args[]) {
	boolean testEnabled = false;
	if (testEnabled) {
	//performTest();
	} else {
	DateFormat format = new SimpleDateFormat("YYYY-M-d:H:m:s:S");
	System.out.println(format.format(new Date()));
	int num = -1235;
	System.out.println("output is:" + reverse(num));
	System.out.println(format.format(new Date()));
	}
	}
	public static int reverse1(int x) {
	if (x >= 0 && x < 10) {
	return x;
	}
	String sresult = "";
	String snum = String.valueOf(x);
	boolean isNegative = false;
	int result = 0;
	if (x < 0) {
	isNegative = true;
	snum = String.valueOf(-x);
	}
	for (int i = snum.length() - 1; i >= 0; i--) {
	sresult += String.valueOf(snum.charAt(i));
	}
	try {
	result = Integer.parseInt(sresult);
	} catch (NumberFormatException nex) {
	result = 0;
	}
	if (result > Integer.MAX_VALUE) {
	return 0;
	}
	if (isNegative) {
	return -result;
	} else {
	return result;
	}
	}
	public static long reverse(int x){
	boolean isNegative = x<0;
	long num = x;
	if(isNegative)
	num = -x;
	if (num < 10 && num>=0)//reverse of single digit is always the same
	{
	return num;
	}
	//find the reverse of the number and check if the reverse is equal to it
	long rev = 0;
	long temp = num;
	while (temp > 0) {
	rev = temp % 10 + rev * 10;
	temp /= 10;
	}
	System.out.println("reverse is:" + rev + " number is:" + x);
	return isNegative?-rev:rev;
	}
	/*
	public static void performTest() {
	Map<Integer, Integer> testCases = new HashMap<Integer, Integer>();
	List<String> failedCases = new ArrayList<String>();
	int result = 0;
	testCases.put(123, 321);
	testCases.put(-123, -321);
	testCases.put(10, 1);//not 01
	testCases.put(1000000003, 0);//overflows for 32 bit integer, so return 0, instead
	testCases.put(-2147483648, 0);//overflows for 32 bit integer, so return 0, instead
	for (int testCase : testCases.keySet()) {
	result = reverse(testCase);
	if (result != testCases.get(testCase)) {
	failedCases.add("Failed for:{" + testCase + "} got:" + result + " expected:" + testCases.get(testCase));
	}
	}
	System.out.println("TEST RESULT, Passed:" + (testCases.size() - failedCases.size()) + " failed:" + failedCases.size());
	for (String failure : failedCases) {
	System.err.println(failure);
	}
	}
	*/
	}

view raw ReverseInteger.java hosted with ❤ by GitHub