C of choosing three numbers randomly in AP ++Program probability

Given an array with the number "n", the task is to find the probability that three randomly selected numbers appear in AP.

Example

Input-: arr[] = {　2,3,4,7,1,2,3　}
Output-: The probability that three random numbers are in A.P. is: 0.107692
Input-: arr[] = {　1,　2,　3,　4,　5　}
Output-: The probability that three random numbers are in A.P. is: 0.151515

The following program uses the following methods-

• Input positive integer array

• Calculate the size of the array

• Apply the following formula to find the probability that three random numbers appear in AP

  3 n /（4（n * n) – 1）

• Print Result

Algorithm

Start
Step　1-> Function to calculate the probability that three random numbers are in AP
　　　double probab(int n)
　　　　　　return (3.0　*　n)　/　(4.0　*　(n　*　n)　-　1)
Step　2->In main()
　　　declare an array of elements as int arr[] = {　2,3,4,7,1,2,3　}
　　　calculate the size of an array as int size = sizeof(arr)/sizeof(arr[0])
　　　call the function to calculate probability as probab(size)
Stop

Example

#include <bits/stdc++.h>
using namespace std;
//calculate the probability that three random numbers are in AP
double probab(int n) {
　　　　return (3.0　*　n)　/　(4.0　*　(n　*　n)　-　1);
}
int main() {
　　　　int arr[] = {　2,3,4,7,1,2,3　};
　　　　int size = sizeof(arr);/sizeof(arr[0]);
　　　　cout << "probability that three random numbers are in A.P. is: " << probab(size);
　　　　return 0;
}

Output Result

The probability that three random numbers are in arithmetic progression (A.P.) is: 0.107692