Multiply Strings

标签：multiply strings

Given two numbers represented as strings, return multiplication of the numbers as a string.

Note: The numbers can be arbitrarily large and are non-negative.

 string multiply(string num1, string num2) {

        int lena=num1.length(),lenb=num2.length();

        if(lena==0||lenb==0)

            return "";

        if(num1=="1")

            return num2;

        if(num2=="1")

            return num1;

        if(num1=="0"||num2=="0")

            return "0";

        int cura=lena-1;

        int curb=lenb-1;

        string res(lena+lenb,‘0‘);

        for(int i=cura;i>=0;i--){

            int carry=0;

            for(int j=curb;j>=0;j--){

                int temp=res[i+j+1]-‘0‘+(num1[i]-‘0‘)*(num2[j]-‘0‘)+carry;

                res[i+j+1]=temp%10+‘0‘;

                carry=temp/10;

            }

            res[i]+=carry;//这里本来应该是s[i+j]得到进位数，但因为innerloop后，j=0,

        }

        int pos=res.find_first_not_of(‘0‘);

        if(pos==string::npos)

            return "0";

        return res.substr(pos);

    }

Multiply Strings

标签：multiply strings

原文地址：http://searchcoding.blog.51cto.com/1335412/1694850