content: package class05;
  
  // 测试链接：https://leetcode.com/problems/divide-two-integers
  public class Code03_BitAddMinusMultiDiv {
  
  	public static int add(int a, int b) {
  		int sum = a;
  		while (b != 0) {
  			sum = a ^ b;
  			b = (a & b) << 1;
  			a = sum;
  		}
  		return sum;
  	}
  
  	public static int negNum(int n) {
  		return add(~n, 1);
  	}
  
  	public static int minus(int a, int b) {
  		return add(a, negNum(b));
  	}
  
  	public static int multi(int a, int b) {
  		int res = 0;
  		while (b != 0) {
  			if ((b & 1) != 0) {
  				res = add(res, a);
  			}
  			a <<= 1;
  			b >>>= 1;
  		}
  		return res;
  	}
  
  	public static boolean isNeg(int n) {
  		return n < 0;
  	}
  
  	public static int div(int a, int b) {
  		int x = isNeg(a) ? negNum(a) : a;
  		int y = isNeg(b) ? negNum(b) : b;
  		int res = 0;
  		for (int i = 30; i >= 0; i = minus(i, 1)) {
  			if ((x >> i) >= y) {
  				res |= (1 << i);
  				x = minus(x, y << i);
  			}
  		}
  		return isNeg(a) ^ isNeg(b) ? negNum(res) : res;
  	}
  
  	public static int divide(int a, int b) {
  		if (a == Integer.MIN_VALUE && b == Integer.MIN_VALUE) {
  			return 1;
  		} else if (b == Integer.MIN_VALUE) {
  			return 0;
  		} else if (a == Integer.MIN_VALUE) {
  			if (b == negNum(1)) {
  				return Integer.MAX_VALUE;
  			} else {
  				int c = div(add(a, 1), b);
  				return add(c, div(minus(a, multi(c, b)), b));
  			}
  		} else {
  			return div(a, b);
  		}
  	}
  
  }
  