# Evaluate an array expression with numbers, + and –

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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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

 ` `

Output :

`13 `

Time Complexity : O(n)

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.