Divide large number represented as string

3.7

Given a large number (represented as string) which has to divided by another number (represented as int data type). The large number can be very large which does not even fit in long long in C++. The task is to find division of these numbers.

Examples:

Input : number  = 1260257
        divisor = 37
Output : 34061
(See below diagram)

Input : number  = 12313413534672234
        divisor = 754
Output : 16330787181262

Input : number  = 1248163264128256512
        divisor = 125
Output : 9985306113026052

We have already discussed Multiply Large Numbers represented as Strings.

We use basic school mathematics as shown in below example.

division
Image Source : https://en.wikipedia.org/wiki/Long_division

As the dividend and result can be very large we store them in string. We first take digits which are divisible by number. After this take each digit and store result in string.

// C++ program to implement division with large
// number
#include <bits/stdc++.h>
using namespace std;

// A function to perform division of large numbers
string longDivision(string number, int divisor)
{
    // As result can be very large store it in string
    string ans;
  
    // Find prefix of number that is larger
    // than divisor.
    int idx = 0;
    int temp = number[idx] - '0';
    while (temp < divisor)
       temp = temp * 10 + (number[++idx] - '0');
    
    // Repeatedly divide divisor with temp. After 
    // every division, update temp to include one 
    // more digit.
    while (number.size() > idx)
    {
        // Store result in answer i.e. temp / divisor
        ans += (temp / divisor) + '0';
        
        // Take next digit of number
        temp = (temp % divisor) * 10 + number[++idx] - '0';
    }
    
    // If divisor is greater than number
    if (ans.length() == 0)
        return "0";
    
    // else return ans
    return ans;
}

// Driver program to test longDivison()
int main()
{
    string number = "1248163264128256512";
    int divisor = 125;    
    cout << longDivision(number, divisor);    
    return 0;
}

Output:
9985306113026052

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