leetcode-29 Divide Two Integers

问题描述:

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

If it is overflow, return MAX_INT.

 

问题分析:

转化为位运算与加减法相结合;

注意处理Integer.MIN_VALUE (-2147483648)的特殊情况,此时应当返回Integer.MAX_VALUE(2147483647)


代码:

public class Solution {
   public int divide(int dividend, int divisor) {
    // 处理特殊情况
        if(divisor == 1)
            return dividend;
        if(dividend == Integer.MIN_VALUE && Math.abs(divisor)== 1)
            return Integer.MAX_VALUE;
        // 判断结果的符号
        int sign = (dividend > 0 ^ divisor > 0) ?-1 : 1;
 
        long ans = 0;
        long end = Math.abs((long)dividend);
        long sor = Math.abs((long)divisor);
 
        // 实现除法的核心
        while(end >= sor) {
            long temp = sor;
            long power = 1;
            while((temp << 1) < end) {
                power <<= 1;
                temp  <<= 1;
            }
            ans += power;
            end -= temp;
        }
        return (int)(sign * ans);
   }
}


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