add.cpp

// CPP program to sum two numbers represented two
// arrays.
#include <bits/stdc++.h>
using namespace std;

// Return sum of two number represented by the arrays.
// Size of a[] is greater than b[]. It is made sure
// by the wrapper function
int calSumUtil(int a[], int b[], int n, int m)
{
	// array to store sum.
	int sum[n];

	int i = n - 1, j = m - 1, k = n - 1;

	int carry = 0, s = 0;

	// Until we reach beginning of array.
	// we are comparing only for second array
	// because we have already compare the size
	// of array in wrapper function.
	while (j >= 0)
	{

		// find sum of corresponding element
		// of both arrays.
		s = a[i] + b[j] + carry;
		sum[k] = (s % 10);

		// Finding carry for next sum.
		carry = s / 10;

		k--;
		i--;
		j--;
	}

	// If second array size is less the first
	// array size.
	while (i >= 0)
	{

		// Add carry to first array elements.
		s = a[i] + carry;
		sum[k] = (s % 10);
		carry = s / 10;

		i--;
		k--;
	}

	int ans = 0;

	// If there is carry on adding 0 index elements.
	// append 1 to total sum.
	if (carry)
		ans = 10;

	// Converting array into number.
	for (int i = 0; i <= n - 1; i++)
	{
		ans += sum[i];
		ans *= 10;
	}

	return ans / 10;
}

// Wrapper Function
int calSum(int a[], int b[], int n, int m)
{
	// Making first array which have
	// greater number of element
	if (n >= m)
		return calSumUtil(a, b, n, m);

	else
		return calSumUtil(b, a, m, n);
}

// Driven Program
int main()
{
	int a[] = {9, 3, 9};
	int b[] = {6, 1};

	int n = sizeof(a) / sizeof(a[0]);
	int m = sizeof(b) / sizeof(b[0]);

	cout << calSum(a, b, n, m) << endl;

	return 0;
}