Grouping Countries

People in a group, are sitting in a row numbered from 1 to n. Every has been asked the same question, “How many people of your country are there in the group?” 
The answers provided by the people may be incorrect. People of the same country always sit together. If all answers are correct determine the number of distinct countries else print “Invalid Answer”.

Examples:  

Input : ans[] = {1, 3, 2, 2}
Output : Invalid Answer
The second person says there are 3 
people from his country however
the person sitting next to him says
there are 2 people. Hence this is 
an invalid answer. 

Input : ans[] = {1, 1, 2, 2, 4, 4, 
                            4, 4}
Output : 4
There are 1 person each representing
two distinct countries. In the next 
one there are two people and in the
fourth one there are 4 people from
the same country.

Source : ThoughtWorks Application Qualifier Test 

This is a basic problem that can be solved in linear time. We will take a variable curr_size that tells us the size of the current country being considered. Whatever the size is, next ‘size’ number of people should give the same answer in order for a valid group to be formed. If anyone gives a different answer or there are less that number of people available then the answer is Invalid. Below is the implementation of idea : 

C++

// CPP program to count no of distinct
// countries from a given group of people
#include <iostream>
using namespace std;

void countCountries(int ans[], int N)
{
    int total_countries = 0, i = 0;
    bool invalid = false;

    while (i < N) {
        int curr_size = ans[i];

        // Answer is valid if adjacent sitting
        // num people give same answer
        int num = ans[i];
        while (num > 0) {

            // someone gives different answer
            if (ans[i] != curr_size) {
                cout << "Invalid Answer\n";
                return;
            }
            else
                num--;

            // check next person
            i++;
        }

        // one valid country group has
        // been found
        total_countries++;
    }

    cout << "There are " << total_countries
         << " distinct companies in the group.\n";
}

// driver program to test above function
int main()
{
    int ans[] = { 1, 1, 2, 2, 4, 4, 4, 4 };
    int n = sizeof(ans) / sizeof(ans[0]);
    countCountries(ans, n);
    return 0;
}

Java

// Java program to count no of distinct
// countries from a given group of people

class Country
{
    public static void countCountries(int ans[],
                                      int N)
    {
        int total_countries = 0, i = 0;
        boolean invalid = false;

        while (i < N) {
            int curr_size = ans[i];

            // Answer is valid if adjacent sitting
            // num people give same answer
            int num = ans[i];
            while (num > 0) {

            // someone gives different answer
            if (ans[i] != curr_size) {
                System.out.print( "Invalid Answer\n" );
                return;
            }
            else
                num--;

            // check next person
            i++;
        }

        // one valid country group has
        // been found
        total_countries++;
        }

        System.out.print( "There are " + total_countries +
            " distinct companies in the group.\n" );
    }

    // driver code
    public static void main(String[] args)
    {
        int ans[] = { 1, 1, 2, 2, 4, 4, 4, 4 };
        int n = 8;
        countCountries(ans, n);
    }
}

// This code is contributed by rishabh_jain

Python3

# Python3 program to count no of distinct
# countries from a given group of people

def countCountries(ans, N):
    total_countries = 0
    i = 0
    invalid = 0

    while (i < N) :
        curr_size = ans[i]

        # Answer is valid if adjacent sitting
        # num people give same answer
        num = ans[i]
        while (num > 0) :

            # someone gives different answer
            if (ans[i] != curr_size) :
                print("Invalid Answer")
                return;
            else:
                num = num - 1

            # check next person
            i = i + 1

        # one valid country group has
        # been found
        total_countries = total_countries + 1;

    print ("There are ", total_countries,
          " distinct companies in the group.")

# Driven code
ans = [ 1, 1, 2, 2, 4, 4, 4, 4 ];
n = len(ans);
countCountries(ans, n);

# This code is contributed by "rishabh_jain".

C#

// C# program to count no. of distinct
// countries from a given group of people
using System;

class Country {

    // function to count no. of distinct
    // countries from a given group of people
    public static void countCountries(int []ans,
                                      int N)
    {
        int total_countries = 0, i = 0;


        while (i < N) {
            int curr_size = ans[i];

            // Answer is valid if adjacent sitting
            // num people give same answer
            int num = ans[i];
            while (num > 0) {

            // someone gives different answer
            if (ans[i] != curr_size) {
                Console.Write( "Invalid Answer\n" );
                return;
            }
            else
                num--;

            // check next person
            i++;
        }

        // one valid country group
        // has been found
        total_countries++;
        }

        Console.Write("There are " + total_countries +
                      " distinct companies in the group.\n" );
    }

    // Driver Code
    public static void Main()
    {
        int []ans = { 1, 1, 2, 2, 4, 4, 4, 4 };
        int n = 8;
        countCountries(ans, n);
    }
}

// This code is contributed by nitin mittal

PHP

<?php
// PHP program to count no of distinct
// countries from a given group of people

function countCountries($ans, $N)
{
    $total_countries = 0;
    $i = 0;
    $invalid = false;

    while ($i < $N)
    {
        $curr_size = $ans[$i];

        // Answer is valid if adjacent sitting
        // num people give same answer
        $num = $ans[$i];
        while ($num > 0)
        {

            // someone gives different
            // answer
            if ($ans[$i] != $curr_size)
            {
                echo"Invalid Answer\n";
                return;
            }
            else
                $num--;

            // check next person
            $i++;
        }

        // one valid country group has
        // been found
        $total_countries++;
    }

    echo "There are " , $total_countries
        , " distinct companies in the group.\n";
}

    // Driver Code
    $ans = array(1, 1, 2, 2, 4, 4, 4, 4 );
    $n = sizeof($ans);
    countCountries($ans, $n);

// This code is contributed by nitin mittal.
?>

Javascript

<script>

// JavaScript program to count no of distinct
// countries from a given group of people
function countCountries(ans, N)
{
    let total_countries = 0, i = 0;
    let invalid = false;

    while (i < N)
    {
        let curr_size = ans[i];

        // Answer is valid if adjacent sitting
        // num people give same answer
        let num = ans[i];
        while (num > 0)
        {

            // Someone gives different answer
            if (ans[i] != curr_size)
            {
                document.write( "Invalid Answer\n" );
                return;
            }
            else
                num--;

            // Check next person
            i++;
        }

        // One valid country group has
        // been found
        total_countries++;
    }
    document.write("There are " + total_countries +
                   " distinct companies in the group.\n" );
}

// Driver Code
let ans = [ 1, 1, 2, 2, 4, 4, 4, 4 ];
let n = 8;

countCountries(ans, n);

// This code is contributed by sanjoy_62

</script>

Output: 

There are 4 distinct companies in the group.