Java for LeetCode 029 Divide Two Integers

Divide two integers without using multiplication, division and mod operator.

If it is overflow, return MAX_INT.

解题思路：

既然不呢个用乘除和取模运算，只好采用移位运算，可以通过设置一个length代表divisor向左的做大移位数，直到大于dividend，然后对length做一个循环递减，dividend如果大于divisor即进行减法运算，同时result加上对应的值，注意边界条件，JAVA实现如下：

static public int divide(int dividend, int divisor) {
		if (divisor == 0)
			return Integer.MAX_VALUE;
		boolean isNeg = dividend < 0;
		if (divisor < 0)
			isNeg = !isNeg;
		int length = 0;
		long longdividend = Math.abs((long) dividend);
		long longdivisor = Math.abs((long) divisor), result = 0;
		while (longdividend >= longdivisor) {
			longdivisor = longdivisor << 1;
			length++;
		}
		while (length >= 0) {
			if (longdividend >= longdivisor) {
				result += Math.pow(2, length);
				longdividend -= longdivisor;
			}
			longdivisor = longdivisor >> 1;
			length--;
		}
		if (result > Integer.MAX_VALUE && !isNeg)
			result = (long) Integer.MAX_VALUE;
		return isNeg ? -(int) result : (int) result;
	}