[Solved] Without Adjacent Contest Problem

Without Adjacent: Given an array arr[] of N positive integers. The task is to find a subsequence with maximum sum such that there should be no adjacent elements from the array in the subsequence.

Without Adjacent Contest

Input:
First line of input contains number of testcases T. For each testcase, first line of input contains size of array N. Next line contains N elements of the array space seperated.

Output:
For each testcase, print the maximum sum of the subsequence.

Constraints:
1 <= T <= 100
1 <= N <= 10⁶
1 <= arr[i] <= 10⁶

Example:
Input:
2
3
1 2 3
3
1 20 3

Output:
4
20

Explanation:
Testcase 1: Elements 1 and 3 form a subsequence with maximum sum and no elements in the subsequence are adjacent in the array.
Testcase 2: Element 20 from the array forms a subsequence with maximum sum.

Solution:

import java.util.*;
import java.lang.*;
import java.io.*;

public class WithoutAdjacent {
    static class FastReader{
        BufferedReader br;
        StringTokenizer st;
        public FastReader(){
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        String next(){
            while (st == null || !st.hasMoreElements()){
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
        String nextLine(){
            String str = "";
            try {
                str = br.readLine();
            }catch (IOException e){
                e.printStackTrace();
            }
            return str;
        }
        int nextInt(){
            return Integer.parseInt(next());
        }
    }
    static int findSubArrayWithMinSum(int[] arr, int i , int j){
        int min = Integer.MIN_VALUE;
        int maxElement = arr[0];
        for (int k = 0; k < j; k++) {
            int currSum =  arr[k];
            maxElement = Math.max(maxElement,arr[k]);
            for (int l = k+2; l < j; l+=2) {
                currSum+=arr[l];
            }
            min = Math.max(currSum,min);
        }
        return Math.max(min,maxElement);
    }
    public static void main(String[] args) {
        FastReader fr = new FastReader();
        int t = fr.nextInt();
        while (t-->0){
            int n = fr.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = fr.nextInt();
            }

            long x = arr[0];
            long y = 0;
            long res;

            for(int i=1;i<n;i++)
            {
                res = Math.max(x, y);
                x = y + arr[i];
                y = res;
            }
            System.out.println((long)Math.max(x,y));
        }
    }
}

def withoutAdjacent(arr): 
    incl = 0
    excl = 0
     
    for i in arr: 
          
        # Current max excluding i (No ternary in  
        # Python) 
        new_excl = excl if excl>incl else incl 
         
        # Current max including i 
        incl = excl + int(i)
        excl = new_excl 
      
    # return max of incl and excl 
    return (excl if excl>incl else incl) 

if __name__ == '__main__':
    t = int(input())
    for c in range(t):
        N = int(input())
        arr = input().strip().split()
        print (withoutAdjacent(arr))

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