LeetCode 29.两数相除 C#

两数相除

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思路

• 不能用乘除，那就用加法。加了多少次，次数就是商。
• 用递归和二分法进行加操作，具体见代码
• 数值溢出可用long类型来解决，通过判断long变量的值是否大于int.MaxValue,来决定返回值

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代码

public class Solution {
    public int Divide(int dividend, int divisor) {
        bool isPositive=true;
        if(dividend<0&&divisor>0 || dividend>0&&divisor<0){
            isPositive=false;
        }
        long ldividend = Math.Abs((long)dividend);
        long ldivisor=Math.Abs((long)divisor);
        long result=divide(ldividend,ldivisor);
        if(result>int.MaxValue){
            return isPositive?int.MaxValue:int.MinValue;
        }
        return isPositive?(int)result:-(int)result;
    }
    
    public long divide(long dividend,long divisor){
        if(dividend<divisor) return 0;
        long sum=divisor;
        long result=1;
        while(dividend>sum+sum){
            sum +=sum;
            result +=result;
        }
        return result+divide(dividend-sum,divisor);
    }
}

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