package com.interview.array;

import java.util.Arrays;

/**
 * Date 12/31/2015
 * @author Tushar Roy
 *
 * Given an array of positive and negative integers arrange them alternatively maintaining initial order.
 * If there are more +ve or -ve integer then push them to the end together.
 *
 * Time complexity is O(n)
 * Space complexity is O(1)
 *
 * http://www.geeksforgeeks.org/rearrange-array-alternating-positive-negative-items-o1-extra-space/
 */
public class PositiveAndNegativeNumberAlternativelyMaintainingOrder {

    public void rearrange(int input[]) {

        for (int i = 0; i < input.length; i++) {
            if (i % 2 == 0 && input[i] >= 0) {
                int indexOfNextNegative = findNext(input, i + 1, false);
                if (indexOfNextNegative == -1) {
                    return;
                } else {
                    rightRotate(input, i, indexOfNextNegative);
                }
            } else if (i % 2 != 0 && input[i] < 0) {
                int indexOfNextPositive = findNext(input, i + 1, true);
                if (indexOfNextPositive == -1) {
                    return;
                } else {
                    rightRotate(input, i, indexOfNextPositive);
                }
            }
        }
    }

    private int findNext(int input[], int start, boolean isPositive) {
        for (int i = start; i < input.length; i++) {
            if ((isPositive && input[i] >= 0) || (!isPositive && input[i] < 0)) {
                return i;
            }
        }
        return -1;
    }

    private void rightRotate(int input[], int start, int end) {
        int t = input[end];
        for (int i = end; i > start; i--) {
            input[i] = input[i - 1];
        }
        input[start] = t;
    }

    public static void main(String args[]) {
        int input[] = {-5, -2, 5, 2, 4, 7, 1, 8, 0, -8};
        PositiveAndNegativeNumberAlternativelyMaintainingOrder pss = new PositiveAndNegativeNumberAlternativelyMaintainingOrder();
        pss.rearrange(input);
        Arrays.stream(input).forEach(i -> System.out.print(i + " "));
    }
}