求助第4、5点TLE

#include<bits/stdc++.h>
using namespace std;
int main()
{
	char a1[101],b1[101];
	int a[101],b[101],c[10001],lena,lenb,lenc,i,j,x;
	memset(a,0,sizeof(a));
	memset(b,0,sizeof(b));
	memset(c,0,sizeof(c));
	scanf("%s",a1);
	scanf("%s",b1);
	lena = strlen(a1);
	lenb = strlen(b1);
	for(i = 0;i <= lena - 1;i++)
	{
		a[lena-i] = a1[i]-48;
	}
	for(i = 0;i <= lenb - 1;i++)
	{
		b[lenb-i] = b1[i]-48;
	}
	for(i = 1;i<=lena;i++)
	{
		x = 0;
		for(j = 1; j<=lenb;j++)
		{
			c[i + j - 1] = a[i] * b[j] + x + c[i + j - 1];
			x = c[i + j - 1]/ 10;
			c[i + j - 1]%= 10;
		}
		c[i + lenb] = x;
	}
	lenc = lena + lenb;
	while(c[lenc] == 0 && lenc > 1)
	{
		lenc--;
	}
	for(i = lenc;i>=1;i--)
	{
		cout << c[i];
	}
	cout << endl;
	return 0;
}