package class07;

import java.util.Arrays;
import java.util.HashSet;

public class Code04_Power2Diffs {

	/*
	 * 给定一个有序数组arr，其中值可能为正、负、0。 返回arr中每个数都平方之后不同的结果有多少种？
	 * 
	 * 给定一个数组arr，先递减然后递增，返回arr中有多少个绝对值不同的数字？
	 * 
	 */

	// 时间复杂度O(N)，额外空间复杂度O(N)
	public static int diff1(int[] arr) {
		if (arr == null || arr.length == 0) {
			return 0;
		}
		HashSet<Integer> set = new HashSet<>();
		for (int cur : arr) {
			set.add(cur * cur);
		}
		return set.size();
	}

	// 时间复杂度O(N)，额外空间复杂度O(1)
	public static int diff2(int[] arr) {
		int N = arr.length;
		int L = 0;
		int R = N - 1;
		int count = 0;
		int leftAbs = 0;
		int rightAbs = 0;
		while (L <= R) {
			count++;
			leftAbs = Math.abs(arr[L]);
			rightAbs = Math.abs(arr[R]);
			if (leftAbs < rightAbs) {
				while (R >= 0 && Math.abs(arr[R]) == rightAbs) {
					R--;
				}
			} else if (leftAbs > rightAbs) {
				while (L < N && Math.abs(arr[L]) == leftAbs) {
					L++;
				}
			} else {
				while (L < N && Math.abs(arr[L]) == leftAbs) {
					L++;
				}
				while (R >= 0 && Math.abs(arr[R]) == rightAbs) {
					R--;
				}
			}
		}
		return count;
	}

	// for test
	public static int[] randomSortedArray(int len, int value) {
		int[] ans = new int[(int) (Math.random() * len) + 1];
		for (int i = 0; i < ans.length; i++) {
			ans[i] = (int) (Math.random() * value) - (int) (Math.random() * value);
		}
		Arrays.sort(ans);
		return ans;
	}

	// for test
	public static void printArray(int[] arr) {
		for (int cur : arr) {
			System.out.print(cur + " ");
		}
		System.out.println();
	}

	public static void main(String[] args) {
		int len = 100;
		int value = 500;
		int testTimes = 200000;
		System.out.println("test begin");
		for (int i = 0; i < testTimes; i++) {
			int[] arr = randomSortedArray(len, value);
			int ans1 = diff1(arr);
			int ans2 = diff2(arr);
			if (ans1 != ans2) {
				printArray(arr);
				System.out.println(ans1);
				System.out.println(ans2);
				System.out.println("Oops!");
				break;
			}
		}
		System.out.println("test finish");
	}

}