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  • leetcode — divide-two-integers

    /**
     * Source : https://oj.leetcode.com/problems/divide-two-integers/
     *
     * Created by lverpeng on 2017/7/12.
     *
     * Divide two integers without using multiplication, division and mod operator.
     *
     * If it is overflow, return MAX_INT.
     */
    public class DevideTwoInt {
    
        /**
         * 不能使用乘、除、求模
         *
         * 可以直接每次减去除数,但是效率较低,那可以使用移位,类似乘法,将除数乘以2的倍数,然后再与被除数做减法
         *
         * @param devident
         * @param devisor
         * @return
         */
        public int devide (int devident, int devisor) {
            long[] sub = new long[32];
            int newDevident = devident < 0 ? -devident : devident;
            int newDevisor = devisor < 0 ? -devisor : devisor;
    
            int count = 0;
            sub[count] = newDevisor;
            int twiceNum = newDevisor;
            while (newDevident > twiceNum) {
                twiceNum = newDevisor << count;
                sub[count] = twiceNum;
                count ++;
            }
            count --;
    
            int remainder = newDevident;
            int result = 0;
            while (remainder >= newDevisor) {
                if (remainder >= sub[count]) {
                    remainder -= sub[count];
                    result = result + (1 << count);
                } else {
                    count --;
                }
            }
    
            return (devident > 0 ^ devisor > 0) ? -result : result;
        }
    
        public static void main(String[] args) {
            DevideTwoInt devideTwoInt = new DevideTwoInt();
            System.out.println(devideTwoInt.devide(-100, 10));
            System.out.println(devideTwoInt.devide(-100, 9));
            System.out.println(devideTwoInt.devide(-100, -9));
            System.out.println(devideTwoInt.devide(100, 9));
            System.out.println(devideTwoInt.devide(0, 9));
        }
    
    }
    
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  • 原文地址:https://www.cnblogs.com/sunshine-2015/p/7420365.html
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