[Solved] Which of the following C functions correctly returns the first prime number found in an integer array, or -1 if none is found, using return inside a loop? | C

C - Loop Control Statements

Which of the following C functions correctly returns the first prime number found in an integer array, or -1 if none is found, using return inside a loop?

A

<pre>int firstPrime(int arr[], int n) {
  int prime = -1;
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      prime = arr[i];
  }
  return prime;
}</pre>

B

<pre>int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      return arr[i];
  }
  return -1;
}</pre>

C

<pre>int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      break;
  }
  return arr[i];
}</pre>

D

<pre>int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      return i;
  }
  return 0;
}</pre>

Step-by-Step Solution

Solution:

Step 1: Analyze

int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      return arr[i];
  }
  return -1;
}

It loops through the array, returns the first prime number immediately when found, else returns -1 after loop.

Step 2: Analyze

int firstPrime(int arr[], int n) {
  int prime = -1;
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      prime = arr[i];
  }
  return prime;
}

It updates prime but does not return immediately, so it returns the last prime found, not the first.

Step 3: Analyze

int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      break;
  }
  return arr[i];
}

Uses break but then returns arr[i] outside loop; i is out of scope or undefined here.

Step 4: Analyze

int firstPrime(int arr[], int n) {
  for(int i = 0; i < n; i++) {
    if(isPrime(arr[i]))
      return i;
  }
  return 0;
}

Returns index of prime, not the prime number itself, and returns 0 if none found which is incorrect.

Final Answer:

int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return arr[i]; } return -1; }
correctly returns the first prime number or -1 if none found.

Quick Check:
Return inside loop immediately returns first prime [OK]

Quick Trick: Return inside loop returns first match immediately [OK]

Common Mistakes:

Returning index instead of value
Not returning immediately inside loop
Using break without proper return

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More C Quizzes

Which of the following C functions correctly returns the first prime number found in an integer array, or -1 if none is found, using return inside a loop?

Step 1: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return arr[i]; } return -1; }

Step 2: Analyze
int firstPrime(int arr[], int n) { int prime = -1; for(int i = 0; i < n; i++) { if(isPrime(arr[i])) prime = arr[i]; } return prime; }

Step 3: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) break; } return arr[i]; }

Step 4: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return i; } return 0; }

Final Answer:

Quick Check:

Want More Practice?

Which of the following C functions correctly returns the first prime number found in an integer array, or -1 if none is found, using return inside a loop?

Step 1: Analyze int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return arr[i]; } return -1; }

Step 2: Analyze int firstPrime(int arr[], int n) { int prime = -1; for(int i = 0; i < n; i++) { if(isPrime(arr[i])) prime = arr[i]; } return prime; }

Step 3: Analyze int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) break; } return arr[i]; }

Step 4: Analyze int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return i; } return 0; }

Final Answer:

Quick Check:

Want More Practice?

Step 1: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return arr[i]; } return -1; }

Step 2: Analyze
int firstPrime(int arr[], int n) { int prime = -1; for(int i = 0; i < n; i++) { if(isPrime(arr[i])) prime = arr[i]; } return prime; }

Step 3: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) break; } return arr[i]; }

Step 4: Analyze
int firstPrime(int arr[], int n) { for(int i = 0; i < n; i++) { if(isPrime(arr[i])) return i; } return 0; }