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Evaluate an array expression with numbers, + and –
  • Difficulty Level : Basic
  • Last Updated : 09 Nov, 2020

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

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++

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// C++ program to find sum of given array of 
// string type in integer form
#include <bits/stdc++.h>
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[0];
  
    // 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][0];
  
        // 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[0]);   
    cout << calculateSum(arr, n);   
    return 0;
}

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Java

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// 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

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Python 3

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# 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

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C#

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// 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[0];
          
        // 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][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 []arr = { "3", "+", "4", "-",
                           "7", "+", "13" };
        int n = arr.Length; 
          
        Console.Write(calculateSum(arr, n)); 
    }
}
  
// This code in contributed by nitin mittal.

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PHP

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<?php
// php program to find sum of given 
// array of string type in integer form
  
// Function to find the
// sum of given array
function 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 = 2; $i < $n; $i = $i + 2)
    {
        $s = $arr[$i];
          
        // cast to convert 
        // string into integer
        $value = (int)$s;
  
        // Find operator
        $operation = $arr[$i - 1];
  
        // If operator is equal to '+',
        // add value in sum variable 
        // else subtract
        if ($operation == '+')
            $sum += $value;
        else if ($operation == '-')
            $sum -= $value;
    }
    return $sum;
}
  
    // Driver code
    $arr = array("3", "+", "4", "-",
                 "7", "+", "13" );
    $n = sizeof($arr) / sizeof($arr[0]); 
    echo calculateSum($arr, $n); 
  
// This code is contributed by mits 
?>

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Output :



13 

Time Complexity : O(n)


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