# C++ Exercises: Find the first repeating element in an array of integers

## C++ Array: Exercise-24 with Solution

Write a C++ program to find the first repeating element in an array of integers.

**Pictorial Presentation:**

**Sample Solution:**

**C++ Code :**

```
#include<iostream>
using namespace std;
int first_repeating_element(int array1[], int s1)
{
int min_val = -1;
set<int> result;
for (int i = s1 - 1; i >= 0; i--)
{
if (result.find(array1[i]) != result.end())
min_val = i;
else
result.insert(array1[i]);
}
if (min_val != -1)
return array1[min_val];
else
return 0;
}
int main()
{
int array1[] = {3, 1, 5, 1, 5, 7, 9, 7, 9};
int fre;
int s1 = sizeof(array1) / sizeof(array1[0]);
cout << "Original array: ";
for (int i=0; i < s1; i++)
cout << array1[i] <<" ";
fre = first_repeating_element(array1, s1);
cout <<"\nFirst repeating element: " << fre;
return 0;
}
```

Sample Output:

Original array: 3 1 5 1 5 7 9 7 9 First repeating element: 1

**Flowchart: **

**C++ Code Editor:**

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

**Next:** Write a C++ program to find and print all common elements in three sorted arrays of integers.

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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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