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?
For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
java code:
1 /** 2 max int is 2,147,483,647 Integer.MAX_VALUE Integer.MIN_VALUE 3 * */ 4 public class ReverseInt { 5 public static void main(String[] args) { 6 int x = 1534236469; 7 int y = reverse(x); 8 System.out.println(y); 9 } 10 11 /* 12 * runtime: 280ms 13 * */ 14 public static int reverse(int x) { 15 boolean isNeg = x < 0? true: false; 16 long result = 0; // result might overflow 17 int temp = Math.abs(x); 18 if(temp == 0) { 19 return 0; 20 } 21 while(temp > 0 ) { 22 result = result * 10 + temp % 10 ; 23 temp /=10; 24 } 25 if (result > Integer.MAX_VALUE) {return 0;} 26 if(isNeg) { 27 result *= -1; 28 } 29 return (int)result; 30 } 31 }
Reference:
1. http://fisherlei.blogspot.com/2012/12/leetcode-reverse-integer.html
原文：http://www.cnblogs.com/anne-vista/p/4790515.html