29. Divide Two Integers

29. Divide Two Integers

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Given two integers dividend and divisor, divide two integers without using multiplication, division and mod operator.

Return the quotient after dividing dividend by divisor.

The integer division should truncate toward zero.

Example 1:

Input: dividend = 10, divisor = 3
Output: 3

Example 2:

Input: dividend = 7, divisor = -3
Output: -2

Note:

• Both dividend and divisor will be 32-bit signed integers.
• The divisor will never be 0.
• Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 231 − 1 when the division result overflows.

class Solution {
    public int divide(int dividend, int divisor) {
	long result = divideLong(dividend, divisor);
	return result > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)result;
}

// It's easy to handle edge cases when
// operate with long numbers rather than int
public long divideLong(long dividend, long divisor) {
	
	// Remember the sign
	boolean negative = dividend < 0 != divisor < 0;
	
	// Make dividend and divisor unsign
	if (dividend < 0) dividend = -dividend;
	if (divisor < 0) divisor = -divisor;
	
	// Return if nothing to divide
	if (dividend < divisor) return 0;
	
	// Sum divisor 2, 4, 8, 16, 32 .... times
    long sum = divisor;
    long divide = 1;
    while ((sum+sum) <= dividend) {
    	sum += sum;
    	divide += divide;
    }
    
    // Make a recursive call for (devided-sum) and add it to the result
    return negative ? -(divide + divideLong((dividend-sum), divisor)) :
    	(divide + divideLong((dividend-sum), divisor));
}
}

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