【LeetCode】Multiply Strings

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