【leetcode】Multiply Strings

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.

 

 

各个位相乘，保存在数组中，最后再处理进位。

如

123*456

 

  4,5,6

     8,10,12

        12,15,18

________________

   4,13,28,27,18

 

即56088

 

 class Solution {
 public:
     string multiply(string num1, string num2) {
 
         if(num1==""||num2=="") return "";
 
         while(num1[]=='') num1.erase();
         while(num2[]=='') num2.erase();
 
         int n1=num1.size();
         int n2=num2.size();
 
         int *numArr1=new int[n1];
         int *numArr2=new int[n2];
 
         int *result=new int[n1+n2];
         memset(result,,sizeof(int)*(n1+n2));
         for(int i=;i<n1;i++) numArr1[i]=num1[i]-'';
         for(int i=;i<n2;i++) numArr2[i]=num2[i]-'';
 
         for(int i=;i<n1;i++)
         {
             for(int j=;j<n2;j++)
             {
                 result[i+j+]+=numArr1[i]*numArr2[j];
             }
         }
 
         int carry=;
         for(int i=n1+n2-;i>=;i--)
         {
             result[i]+=carry;
             if(result[i]>=)
             {
                 carry=result[i]/;
                 result[i]=result[i]%;
             }
             else
             {
                 carry=;
             }
         }
 
         string resultStr;
         int k=;
         while(result[k]==) k++;
 
         for(int i=k;i<n1+n2;i++)
         {
             resultStr.push_back(result[i]+'');
         }
 
         return resultStr;
     }
 };