Divide Two Integers

最新推荐文章于 2021-05-07 19:18:17 发布

最新推荐文章于 2021-05-07 19:18:17 发布 · 76 阅读

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本文介绍了一种不使用乘法、除法和取余运算符实现整数除法的方法。通过位操作和循环实现了除法功能，并考虑了溢出情况。

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

If it is overflow, return MAX_INT.

public class Solution {
    public int divide(int dividend, int divisor) {
    	int r = 0;
        if (divisor == 0) {
        	return 0;
        }
        if (dividend == Integer.MIN_VALUE && divisor == Integer.MIN_VALUE) {
        	return 1;
        } else if (divisor == Integer.MIN_VALUE) {
        	return 0;
        } else if (dividend == Integer.MIN_VALUE) {
        	if (divisor == -1) {
        		return Integer.MAX_VALUE;
        	}
        	int res = div(add(dividend, 1), divisor);
        	return add(res, div(minus(dividend, multi(res, divisor)), divisor));
        } else {
        	return div(dividend, divisor);
        }
        
    }

	private int minus(int a, int b) {
		// TODO Auto-generated method stub
		return add(a, negNum(b));
	}

	private int multi(int a, int b) {
		// TODO Auto-generated method stub
		int res = 0;
		while (b != 0) {
			if ((b & 1) != 0) {
				res = add(res, a);
			}
			a <<= 1;
			b >>>= 1;
		}
		return res;
	}

	private int div(int a, int b) {
		// TODO Auto-generated method stub
		int x = isNeg(a) ? negNum(a) : a;
		int y = isNeg(b) ? negNum(b) : b;
		int res = 0;
		for (int i = 31; i > -1; i = minus(i, 1)) {
			if ((x >> i) >= y) {
				res |= (1 << i);
				x = minus(x, y << i);
			}
		}
		return isNeg(a) ^ isNeg(b) ? negNum(res) : res;
	}

	private int negNum(int a) {
		// TODO Auto-generated method stub
		return add(~a, 1);
	}

	private boolean isNeg(int a) {
		// TODO Auto-generated method stub
		return a < 0;
	}

	private int add(int a, int b) {
		// TODO Auto-generated method stub
		int sum = a;
		while (b != 0) {
			sum = a ^ b;
			b = (a & b) << 1;
			a = sum;
		}
		return sum;
	}
}

public class Solution {
    public int divide(int dividend, int divisor) {
        if (dividend == 0 || divisor == 0) {  
            return 0;  
        }  
        if (dividend == Integer.MIN_VALUE && divisor == -1) {
        	return Integer.MAX_VALUE;
        }
        boolean isNeg = (dividend > 0 && divisor < 0)  
                || (dividend < 0 && divisor > 0);  
        long a = Math.abs((long) dividend);  
        long b = Math.abs((long) divisor);  
        if (b > a) {  
            return 0;  
        }  
  
        long sum = 0;  
        long pow = 0;  
        int result = 0;  
        while (a >= b) {  
            pow = 1;  
            sum = b;  
            while (sum + sum <= a) {  
                sum += sum;  
                pow += pow;  
            }  
            a -= sum;  
            result += pow;  
        }  
        return isNeg ? -result : result;  
    }
}