CPPLAN03.cpp

#include<bits/stdc++.h>
 
using namespace std;
 
string mul(string a, string b){
    string res="";
    int n=a.length();
    int m=b.length();
    int len=n+m-1;
    int carry=0;
    for(int i=len;i>=0;i--){
        int tmp=0;
        for(int j=n-1;j>=0;j--)
            if(i-j<=m && i-j>=1){
                int a1=a[j]-48;
                int b1=b[i-j-1]-48;
                tmp+=a1*b1;
            }
            tmp+=carry;
            carry=tmp/10;
            res=(char)(tmp%10 + 48)+res;
    }
    while(res.length()>1 && res[0]=='0') res.erase(0,1);
    return res;
}
 
void process(){
    string a,b;
    string res = "";
    cin >> a >> b;
    if ((a[0] == '-' && b[0] != '-') || (a[0] != '-' && b[0] == '-')){
        if (a[0] == '-') a.erase(0,1);
        if (b[0] == '-') b.erase(0,1);
        res += "-";
        res = mul(a,b);
    }
    else{
        if (a[0] == '-') a.erase(0,1);
        if (b[0] == '-') b.erase(0,1);
        res = mul(a,b);
    }
    cout << res << endl;
}
 
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);cout.tie(NULL);
    int T;
    cin >> T;
    while(T--){
        process();
    }
    return 0;
}