Sum of an array of large numbers

Difficulty Level : Hard
Last Updated : 13 Sep, 2020

Given an integer K and an array arr[] consisting of N large numbers in the form of strings, the task is to find the sum of all the large numbers of the array.

Examples:

Input: K = 50, arr[] =
{“01234567890123456789012345678901234567890123456789”,
“01234567890123456789012345678901234567890123456789”,
“01234567890123456789012345678901234567890123456789”,
“01234567890123456789012345678901234567890123456789”,
“01234567890123456789012345678901234567890123456789”}
Output: 116172839461617283946161728394616172839461617283945
Input: K = 10, arr[] = {“1111111111”, “1111111111”, “1111111111”,
“1111111111”, “1111111111”}
Output: 5555555555

Approach: The idea is based on adding the digits at corresponding positions of all the numbers. Create an array result[] of size K + 1 to store the result. Traverse all the strings from the end and keep on adding the digits of all the numbers at the same position and insert it into the corresponding index in result[]. Below are the steps:

Initialize an array result[] to store the summation of numbers.
Iterate over the strings from indices K to 0 and for each index, perform the following operations:
- Traverse all the array elements and calculate the sum of all the digits at the current index, say idx, and store in a variable, say sum.
- Place the digit at one’s place of the above sum at result[idx].
- Store the value of sum / 10 as the carry for the next index.
After repeating the above steps for the entire length of all the array, reverse all the digits stored in result[] to get the resultant summation of the given N numbers.

Below is the implementation of the above approach:

C++

// C++ program for the above approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to print the result of the
// summation of numbers having K-digit
void printResult(vector<int> result)
{
    // Reverse the array to
    // obtain the result
    reverse(result.begin(), result.end());
 
    int i = 0;
 
    while (i < result.size()) {
 
        // Print every digit
        // of the answer
        cout << result[i];
        i++;
    }
}
 
// Function to calculate the total sum
void sumOfLargeNumbers(string v[], int k, int N)
{
    // Stores the array of large
    // numbers in integer format
    vector<vector<int> > x(1000);
 
    for (int i = 0; i < k; i++) {
 
        for (int j = 0; j < N; j++) {
 
            // Convert each element
            // from character to integer
            x[i].push_back(v[i][j] - '0');
        }
    }
 
    // Stores the carry
    int carry = 0;
 
    // Stores the result
    // of summation
    vector<int> result;
 
    for (int i = N - 1; i >= 0; i--) {
 
        // Initialize the sum
        int sum = 0;
 
        for (int j = 0; j < k; j++)
 
            // Calculate sum
            sum += x[j][i];
 
        // Update the sum by adding
        // existing carry
        sum += carry;
        int temp = sum;
 
        // Store the number of digits
        int count = 0;
        while (temp > 9) {
            temp = temp % 10;
 
            // Increase count of digits
            count++;
        }
 
        long long int l = pow(10, count);
        if (l != 1)
 
            // If the number exceeds 9,
            // Store the unit digit in carry
            carry = (double)sum / l;
 
        // Store the rest of the sum
        sum = sum % 10;
 
        // Append digit by digit
        // into result array
        result.push_back(sum);
    }
    while (carry != 0) {
        int a = carry % 10;
 
        // Append result until
        // carry is 0
        result.push_back(a);
        carry = carry / 10;
    }
 
    // Print the result
    printResult(result);
}
 
// Driver Code
int main()
{
    int K = 10;
    int N = 5;
 
    // Given N array of large numbers
    string arr[]
        = { "1111111111", "1111111111",
            "1111111111", "1111111111",
            "1111111111" };
 
    sumOfLargeNumbers(arr, N, K);
    return 0;
}

Java

// Java program for the above approach
import java.util.*;
import java.lang.*;
 
class GFG{
 
// Function to print the result of the
// summation of numbers having K-digit
static void printResult(ArrayList<Integer> result)
{
     
    // Reverse the array to
    // obtain the result
    Collections.reverse(result);
 
    int i = 0;
 
    while (i < result.size())
    {
         
        // Print every digit
        // of the answer
        System.out.print(result.get(i));
        i++;
    }
}
 
// Function to calculate the total sum
static void sumOfLargeNumbers(String v[],
                              int k, int N)
{
     
    // Stores the array of large
    // numbers in integer format
    ArrayList<
    ArrayList<Integer>> x = new ArrayList<>(1000);
 
    for(int i = 0; i < k; i++)
        x.add(new ArrayList<Integer>());
 
    for(int i = 0; i < k; i++)
    {
        for(int j = 0; j < N; j++)
        {
 
            // Convert each element
            // from character to integer
            x.get(i).add(v[i].charAt(j) - '0');
        }
    }
 
    // Stores the carry
    int carry = 0;
 
    // Stores the result
    // of summation
    ArrayList<Integer> result = new ArrayList<>();
 
    for(int i = N - 1; i >= 0; i--)
    {
         
        // Initialize the sum
        int sum = 0;
 
        for(int j = 0; j < k; j++)
 
            // Calculate sum
            sum += x.get(j).get(i);
 
        // Update the sum by adding
        // existing carry
        sum += carry;
        int temp = sum;
 
        // Store the number of digits
        int count = 0;
        while (temp > 9)
        {
            temp = temp % 10;
 
            // Increase count of digits
            count++;
        }
 
        long l = (long)Math.pow(10, count);
        if (l != 1)
         
            // If the number exceeds 9,
            // Store the unit digit in carry
            carry = (int)(sum / l);
 
        // Store the rest of the sum
        sum = sum % 10;
 
        // Append digit by digit
        // into result array
        result.add(sum);
    }
    while (carry != 0)
    {
        int a = carry % 10;
 
        // Append result until
        // carry is 0
        result.add(a);
        carry = carry / 10;
    }
 
    // Print the result
    printResult(result);
}
 
// Driver Code
public static void main (String[] args)
{
    int K = 10;
    int N = 5;
     
    // Given N array of large numbers
    String arr[]  = { "1111111111", "1111111111",
                      "1111111111", "1111111111",
                      "1111111111" };
     
    sumOfLargeNumbers(arr, N, K);
}
}
 
// This code is contributed by offbeat

Python3

# Python3 program for the above approach
 
# Function to prthe result of the
# summation of numbers having K-digit
def printResult(result):
 
    # Reverse the array to
    # obtain the result
    result = result[::-1]
 
    i = 0
    while (i < len(result)):
 
        # Print every digit
        # of the answer
        print(result[i], end = "")
        i += 1
 
# Function to calculate the total sum
def sumOfLargeNumbers(v, k, N):
 
    # Stores the array of large
    # numbers in integer format
    x = [[] for i in range(1000)]
 
    for i in range(k):
        for j in range(N):
 
            # Convert each element
            # from character to integer
            x[i].append(ord(v[i][j]) - ord('0'))
 
    # Stores the carry
    carry = 0
 
    # Stores the result
    # of summation
    result = []
 
    for i in range(N - 1, -1, -1):
 
        # Initialize the sum
        sum = 0
 
        for j in range(k):
 
            # Calculate sum
            sum += x[j][i]
 
        # Update the sum by adding
        # existing carry
        sum += carry
        temp = sum
 
        # Store the number of digits
        count = 0
        while (temp > 9):
            temp = temp % 10
 
            # Increase count of digits
            count += 1
 
        l = pow(10, count)
        if (l != 1):
 
            # If the number exceeds 9,
            # Store the unit digit in carry
            carry = sum / l
 
        # Store the rest of the sum
        sum = sum % 10
 
        # Append digit by digit
        # into result array
        result.append(sum)
 
    while (carry != 0):
        a = carry % 10
 
        # Append result until
        # carry is 0
        result.append(a)
        carry = carry // 10
 
    # Print the result
    printResult(result)
 
# Driver Code
if __name__ == '__main__':
     
    K = 10
    N = 5
 
    # Given N array of large numbers
    arr= [ "1111111111", "1111111111",
           "1111111111", "1111111111",
           "1111111111" ]
 
    sumOfLargeNumbers(arr, N, K)
 
# This code is contributed by mohit kumar 29

C#

// C# program for
// the above approach
using System;
using System.Collections.Generic;
class GFG{
 
// Function to print the result of the
// summation of numbers having K-digit
static void printResult(List<int> result)
{
  // Reverse the array to
  // obtain the result
  result.Reverse();
 
  int i = 0;
 
  while (i < result.Count)
  {
 
    // Print every digit
    // of the answer
    Console.Write(result[i]);
    i++;
  }
}
 
// Function to calculate the total sum
static void sumOfLargeNumbers(String []v,
                              int k, int N)
{  
  // Stores the array of large
  // numbers in integer format
  List<List<int>> x =
            new List<List<int>>(1000);
 
  for(int i = 0; i < k; i++)
    x.Add(new List<int>());
 
  for(int i = 0; i < k; i++)
  {
    for(int j = 0; j < N; j++)
    {
      // Convert each element
      // from character to integer
      x[i].Add(v[i][j] - '0');
    }
  }
 
  // Stores the carry
  int carry = 0;
 
  // Stores the result
  // of summation
  List<int> result = new List<int>();
 
  for(int i = N - 1; i >= 0; i--)
  {
    // Initialize the sum
    int sum = 0;
 
    for(int j = 0; j < k; j++)
 
      // Calculate sum
      sum += x[j][i];
 
    // Update the sum by adding
    // existing carry
    sum += carry;
    int temp = sum;
 
    // Store the number of digits
    int count = 0;
    while (temp > 9)
    {
      temp = temp % 10;
 
      // Increase count of digits
      count++;
    }
 
    long l = (long)Math.Pow(10, count);
    if (l != 1)
 
      // If the number exceeds 9,
      // Store the unit digit in carry
      carry = (int)(sum / l);
 
    // Store the rest of the sum
    sum = sum % 10;
 
    // Append digit by digit
    // into result array
    result.Add(sum);
  }
   
  while (carry != 0)
  {
    int a = carry % 10;
 
    // Append result until
    // carry is 0
    result.Add(a);
     
    carry = carry / 10;
  }
 
  // Print the result
  printResult(result);
}
 
// Driver Code
public static void Main(String[] args)
{
  int K = 10;
  int N = 5;
 
  // Given N array of large numbers
  String []arr  = {"1111111111",
                   "1111111111",
                   "1111111111",
                   "1111111111",
                   "1111111111"};
 
  sumOfLargeNumbers(arr, N, K);
}
}
 
// This code is contributed by Rajput-Ji

Output:

5555555555

Time Complexity: O(N*K)
Auxiliary Space: O(K)

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