c++编写一函数返回任意大的两整数之差

#include <iostream>
using namespace std;

#define N 50
int main()
{
char a[N] ;
char b[N], r[N];
int i, j;
int lenA = 0, lenB = 0;
int offset;
bool longA, bigA;
int lenMin, lenMax;
int flag;

// freopen("e:\\d.txt", "r", stdin);
cout << "Please input num 1: \n";
cin >> a;
cout << "Please input num 2: \n";
cin >> b;

i = 0;
while(a[i] != 0)
{
lenA++;
i++;
}
i = 0;
while(b[i] != 0)
{
lenB++;
i++;
}
offset = lenA - lenB;
longA = (offset >= 0 ? true : false);
offset = (longA == true ? offset : -offset);
lenMax = (lenA >= lenB ? lenA : lenB);
char * p;

p = (longA == true ? b : a);
lenMin = (longA == true ? lenB: lenA);
for (i = lenMin; i >= 0