Leetcode Multiply Strings

题目链接：https://oj.leetcode.com/problems/multiply-strings/

Multiply Strings

Total Accepted: 8084 Total
Submissions: 40447My Submissions

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.

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模拟大整数乘法，用经典的算法即可解决问题。

class Solution {
public:
string multiply(string num1, string num2) {
if(num1=="0"||num2=="0") return "0";
int l1=num1.size(),l2=num2.size();
int *n1=new int [l1],*n2=new int [l2],*res=new int [l1+l2];
memset(res,0,sizeof(int)*(l1+l2));
for(int i=0;i<l1;i++) n1[i]=num1[i]-'0';
for(int i=0;i<l2;i++) n2[i]=num2[i]-'0';
for(int i=0;i<l1;i++)
for(int j=0;j<l2;j++)
res[i+j+1]+=n1[i]*n2[j];
string ans="";
for(int k=l1+l2-1;k>=0;k--){
if(k>0) res[k-1]+=res[k]/10;
res[k]%=10;
ans=char(res[k]+'0')+ans;
}
ans=ans[0]=='0'?ans.substr(1):ans;
delete []n1;
delete []n2;
delete []res;
return ans;
}
};