HackerRank Zig Zag Sequence problem solution

In this HackerRank Zig Zag Sequence problem solution, the task is to debug the existing code to successfully execute all provided test files.

Given an array of n distinct integers, transform the array into a zig-zag sequence by permuting the array elements. A sequence will be called a zig-zag sequence if the first k elements in the sequence are in increasing order and the last k elements are in decreasing order, where k = (n + 1)/2. You need to find the lexicographically smallest zig-zag sequence of the given array.

Problem solution in Python.

def findZigZagSequence(a, n):
    a.sort()
    mid = int(n / 2)
    a[mid], a[n-1] = a[n-1], a[mid]

    st = mid + 1
    ed = n - 2
    while(st <= ed):
        a[st], a[ed] = a[ed], a[st]
        st = st + 1
        ed = ed - 1

    for i in range (n):
        if i == n-1:
            print(a[i])
        else:
            print(a[i], end = ' ')
    return

test_cases = int(input())
for cs in range (test_cases):
    n = int(input())
    a = list(map(int, input().split()))
    findZigZagSequence(a, n)

Problem solution in Java.

import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;
public class Main {
    
    public static void main (String[] args) throws java.lang.Exception {
        Scanner kb = new Scanner(System.in);
        int test_cases = kb.nextInt();
        for(int cs = 1; cs <= test_cases; cs++){
            int n = kb.nextInt();
             int a[] = new int[n];
            for(int i = 0; i < n; i++){
                a[i] = kb.nextInt();
            }
            findZigZagSequence(a, n);
        }
   }
   
    public static void findZigZagSequence(int [] a, int n){
        Arrays.sort(a);
        int mid = n/2;
        int temp = a[mid];
        a[mid] = a[n - 1];
        a[n - 1] = temp;
    
        int st = mid + 1;
        int ed = n - 2;
        while(st <= ed){
            temp = a[st];
            a[st] = a[ed];
            a[ed] = temp;
            st = st + 1;
            ed = ed - 1;
        }
        for(int i = 0; i < n; i++){
            if(i > 0) System.out.print(" ");
            System.out.print(a[i]);
        }
        System.out.println();
    }
}

Problem solution in C++.

#include <bits/stdc++.h>
using namespace std;

void findZigZagSequence(vector < int > a, int n){
    sort(a.begin(), a.end());
    int mid = (n + 1)/2 - 1; //change 1
    swap(a[mid], a[n-1]);

    int st = mid + 1;
    int ed = n - 2; //change 2
    while(st <= ed){
        swap(a[st], a[ed]);
        st = st + 1;
        ed = ed - 1; //change 3
    }
    for(int i = 0; i < n; i++){
        if(i > 0) cout << " ";
        cout << a[i];
    }
    cout << endl;
}

int main() {
    int n, x;
    int test_cases;
    cin >> test_cases;

    for(int cs = 1; cs <= test_cases; cs++){
        cin >> n;
        vector < int > a;
        for(int i = 0; i < n; i++){
            cin >> x;
            a.push_back(x);
        }
        findZigZagSequence(a, n);
    }
}

Problem solution in Python.

Problem solution in Java.

Problem solution in C++.

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