29. Divide Two Integers

 1 public class Solution {
 2     public int divide(int dividend, int divisor) {
 3         if (divisor == 0) return Integer.MAX_VALUE;
 4         if (dividend == 0 || dividend > 0 && divisor > 0 && dividend < divisor || dividend < 0 && divisor < 0 && dividend > divisor) return 0;
 5         if (divisor == 1) return dividend;
 6         else if (divisor == -1) {
 7             if (dividend == Integer.MIN_VALUE) return Integer.MAX_VALUE;
 8             return -dividend;
 9         }
10         if (dividend == divisor) return 1;
11         else if (dividend == -divisor) return -1;
12 
13         int sign = 1;
14 
15         if (dividend > 0 && divisor < 0) {
16             divisor = -divisor;
17             sign = -1;
18         } else if (dividend < 0 && divisor > 0) {
19             dividend = -dividend;
20             sign = -1;
21         }
22 
23         int initDivisor = divisor;
24         int quotient = 0;
25         int times = 0;
26 
27         while (dividend >= initDivisor) {
28             while (dividend > divisor) {
29                 divisor <<= 1;
30                 if (times == 0) times = 1;
31                 else             times <<= 1;
32             }
33             quotient += times;
34             dividend -= divisor >> 1;
35             divisor = initDivisor;
36             times = 0;
37         }
38         return sign == 1? quotient: -quotient;
39     }
40 }