Thursday, 18 August 2016

Maximum Sub Array


Given an array of N elements, find the maximum possible sum of a 1. contiguous subarray 2. non-contiguous (not necessarily contiguous) subarray. Empty subarrays should not be considered.

Sample Run

input:
2
6
-1 -2 -3 -4 -5 -6
8
1 -16 15 23 -53 75 80 -24
output:
-1 -1
155 194

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {
   
    //standard max function
    static int max(int x, int y) { return (y > x) ? y : x; }
   
    //modified version of Kadane's algorithm
    static int maxSubarrayContiguous(int[] arr, int indexMax) {
        //takes in first value just so it has _something_
        int maxSoFar = arr[0];
        int currMax = arr[0];
       
           for (int i = 1; i < indexMax; i++) {
                currMax = max(arr[i], currMax + arr[i]);
                maxSoFar = max(maxSoFar, currMax);
           }
           return maxSoFar;
        }
   
    static int maxSubarrayNonContiguous(int[] arr, int indexMax) {
        int sumMax = 0;
        int max = arr[0];
        boolean negArray = true;
        int res = 0;
        for (int i = 0; i < indexMax; i++) {
            //add all positive numbers
            if (arr[i] >= 0) {
                sumMax += arr[i];
                negArray = false;
            }
            //find the smallest negative number
            if (arr[i] >= max) { max = arr[i];}
        }
   
        if (negArray == false)
            res = sumMax;
        //if the array consists of all negative numbers
        //return the smallest number
        if (negArray)
            res = max;
       
        return res;
       
    }
   

    public static void main(String[] args) {
       
        Scanner in = new Scanner(System.in);
        //array to store continous solutions
        int[] testSolutionsC = new int[10];
        //array to store non-continuous
        int[] testSolutionsNC = new int[10];
        int resC;
        int resNC;
        int runs;
        runs = Integer.parseInt(in.nextLine());
       
        //go through the amount of solutions
        for (int i = 0; i < runs; i++) {
            String inputString;
            int[] arr = new int[100000];
            int indexMax = Integer.parseInt(in.nextLine());
           
            //tokenize input values;
            //all entries are separated by a space
            inputString = in.nextLine();
            int arrIndex=0;
            StringTokenizer st = new StringTokenizer(inputString);
            while(st.hasMoreTokens()) {
                arr[arrIndex] = Integer.parseInt(st.nextToken());
                arrIndex++;
            }
           
            //continuous solution
            resC = maxSubarrayContiguous(arr, indexMax);
            //non-continuous solution
            resNC = maxSubarrayNonContiguous(arr, indexMax);
           
            //add continuous solutions to array
            testSolutionsC[i] = resC;
            //add non-continuous solutions to array
            testSolutionsNC[i] = resNC;
           
        }
       
        //print out entries
        for(int i = 0; i < runs; i++) {
            System.out.print(testSolutionsC[i] + " ");
            System.out.print(testSolutionsNC[i]);
            System.out.println();
        }
       
    }
}
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