# C++ Exercises: Find the missing element from two given arrays of integers except one element

## C++ Array: Exercise-22 with Solution

Write a C++ program to find the missing element from two given arrays of integers except one element.

**Sample Solution:**

**C++ Code :**

```
#include <iostream>
using namespace std;
int findMissing(int array1[], int array2[], int s1, int s2)
{
int result = 0;
for (int i=0; i<s1; i++)
result = result^array1[i];
for (int i=0; i<s2; i++)
result = result^array2[i];
return result;
}
int main()
{
int array1[] = {3, 1, 5, 7, 9};
int array2[] = {3, 7, 5, 9};
int mn;
int s1 = sizeof(array1) / sizeof(array1[0]);
int s2 = sizeof(array2) / sizeof(array2[0]);
if (s1 != s2-1 && s2 != s1-1)
{
cout << "Invalid Input";
return 0;
}
cout << "Original arrays: ";
cout << "\nFirst array: ";
for (int i=0; i < s1; i++)
cout << array1[i] <<" ";
cout << "\nSecond array: ";
for (int i=0; i < s2; i++)
cout << array2[i] <<" ";
mn = findMissing(array1, array2, s1, s2);
cout <<"\nMissing number: " << mn;
return 0;
}
```

Sample Output:

Original arrays: First array: 3 1 5 7 9 Second array: 3 7 5 9 Missing number: 1

**Flowchart: **

**C++ Code Editor:**

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**Next:** Write a C++ program to find the element that appears once in an array of integers and every other element appears twice.

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## C++ Programming: Tips of the Day

**Can I assume (bool)true == (int)1 for any C++ compiler?**

According to the standard, you should be safe with that assumption. The C++ bool type has two values - true and false with corresponding values 1 and 0.

The thing to watch about for is mixing bool expressions and variables with BOOL expression and variables. The latter is defined as FALSE = 0 and TRUE != FALSE, which quite often in practice means that any value different from 0 is considered TRUE.

A lot of modern compilers will actually issue a warning for any code that implicitly tries to cast from BOOL to bool if the BOOL value is different than 0 or 1

Ref: https://bit.ly/3PWhs5N

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