# Evaluate an array expression with numbers, + and –

• Difficulty Level : Basic
• Last Updated : 27 May, 2021

Given an array arr[] of string type which consists of strings “+”, “-” and Numbers. Find the sum of the given array.
Examples :

```Input : arr[] = {"3", "+", "4", "-", "7", "+", "13"}
Output : Value = 13
The value of expression 3+4-7+13 is 13.

Input : arr[] = { "2", "+", "1", "-8", "+", "13"}
Output : Value = 8```

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Approach :
1) First of all, initialize the sum i.e, sum = 0.
2) Start traversing the array.
3) As there is string of numbers at every even position of the array, so convert this string into integer and store in a variable value by using stoi function in C++
4) As there is operator at every odd position, check if the operator is ‘+’ or ‘-‘. If it is ‘+’, then add the value to the sum, else subtract from the sum.
5) Finally, return the sum obtained.
Below is the implementation of the above approach :

## C++

 `// C++ program to find sum of given array of``// string type in integer form``#include ``using` `namespace` `std;` `// Function to find the sum of given array``int` `calculateSum(string arr[], ``int` `n)``{  ``    ``// if string is empty``    ``if` `(n == 0)``       ``return` `0;` `    ``string s = arr;` `    ``// stoi function to convert``    ``// string into integer``    ``int` `value = stoi(s);``    ``int` `sum = value;` `    ``for` `(``int` `i = 2; i < n; i = i + 2)``    ``{``        ``s = arr[i];` `        ``// stoi function to convert``        ``// string into integer``        ``int` `value = stoi(s);` `        ``// Find operator``        ``char` `operation = arr[i - 1];` `        ``// If operator is equal to '+',``        ``// add value in sum variable``        ``// else subtract``        ``if` `(operation == ``'+'``)``            ``sum += value;``        ``else``            ``sum -= value;``    ``}``    ``return` `sum;``}` `// Driver Function``int` `main()``{``    ``string arr[] = { ``"3"``, ``"+"``, ``"4"``, ``"-"``,``                     ``"7"``, ``"+"``, ``"13"` `};``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr);  ``    ``cout << calculateSum(arr, n);  ``    ``return` `0;``}`

## Java

 `// Java program to find sum of given array of``// string type in integer form``import` `java.io.*;` `class` `GFG {``    ` `    ``// Function to find the sum of given array``    ``public` `static` `int` `calculateSum(String arr[], ``int` `n)``    ``{``        ``// if string is empty``        ``if` `(n == ``0``)``        ``return` `0``;``        ``String s = arr[``0``];``        ` `        ``// parseInt function to convert``        ``// string into integer``        ``int` `value = Integer.parseInt(s);``        ``int` `sum = value;``    ` `        ``for` `(``int` `i = ``2``; i < n; i = i + ``2``)``        ``{``            ``s = arr[i];``    ` `            ``// parseInt function to convert``            ``// string into integer``            ``value = Integer.parseInt(s);``    ` `            ``// Find operator``            ``char` `operation = arr[i - ``1``].charAt(``0``);``    ` `            ``// If operator is equal to '+',``            ``// add value in sum variable``            ``// else subtract``            ``if` `(operation == ``'+'``)``                ``sum += value;``            ``else``                ``sum -= value;``        ``}``        ``return` `sum;``    ``}` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``String arr[] = { ``"3"``, ``"+"``, ``"4"``, ``"-"``,``                        ``"7"``, ``"+"``, ``"13"` `};``        ``int` `n = arr.length;``        ``System.out.println( calculateSum(arr, n));``    ``}``}` `// This code in contributed by Upendra bartwal`

## Python 3

 `# Python3 program to find sum of given``# array of string type in integer form` `# Function to find the sum of given array``def` `calculateSum(arr, n):` `    ``# if string is empty``    ``if` `(n ``=``=` `0``):``        ``return` `0` `    ``s ``=` `arr[``0``]` `    ``# stoi function to convert``    ``# string into integer``    ``value ``=` `int``(s)``    ``sum` `=` `value` `    ``for` `i ``in` `range``(``2` `, n, ``2``):``    ` `        ``s ``=` `arr[i]` `        ``# stoi function to convert``        ``# string into integer``        ``value ``=` `int``(s)` `        ``# Find operator``        ``operation ``=` `arr[i ``-` `1``][``0``]` `        ``# If operator is equal to '+',``        ``# add value in sum variable``        ``# else subtract``        ``if` `(operation ``=``=` `'+'``):``            ``sum` `+``=` `value``        ``else``:``            ``sum` `-``=` `value``    ` `    ``return` `sum` `# Driver Function``arr ``=` `[``"3"``, ``"+"``, ``"4"``, ``"-"``,``"7"``, ``"+"``, ``"13"``]``n ``=` `len``(arr)``print``(calculateSum(arr, n))` `# This code is contributed by Smitha`

## C#

 `// C# program to find sum of given array of``// string type in integer form``using` `System;` `class` `GFG {``    ` `    ``// Function to find the sum of given array``    ``public` `static` `int` `calculateSum(``string` `[]arr,``                                          ``int` `n)``    ``{``        ` `        ``// if string is empty``        ``if` `(n == 0)``            ``return` `0;``        ``string` `s = arr;``        ` `        ``// parseInt function to convert``        ``// string into integer``        ``int` `value = ``int``.Parse(s);``        ``int` `sum = value;``    ` `        ``for` `(``int` `i = 2; i < n; i = i + 2)``        ``{``            ``s = arr[i];``    ` `            ``// parseInt function to convert``            ``// string into integer``            ``value = ``int``.Parse(s);``    ` `            ``// Find operator``            ``char` `operation = arr[i - 1];``    ` `            ``// If operator is equal to '+',``            ``// add value in sum variable``            ``// else subtract``            ``if` `(operation == ``'+'``)``                ``sum += value;``            ``else``                ``sum -= value;``        ``}``        ` `        ``return` `sum;``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main ()``    ``{``        ``string` `[]arr = { ``"3"``, ``"+"``, ``"4"``, ``"-"``,``                           ``"7"``, ``"+"``, ``"13"` `};``        ``int` `n = arr.Length;``        ` `        ``Console.Write(calculateSum(arr, n));``    ``}``}` `// This code in contributed by nitin mittal.`

## PHP

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## Javascript

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Output :

`13 `

Time Complexity : O(n)

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