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package leo.class03_04;
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/**
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* @author Leo
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* @ClassName BiggerThanRightTwice
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* @DATE 2020/11/24 2:10 下午
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* @Description 对于每个数num，求有多少个后面的数 * 2 依然<左面的数，求总个数
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*/
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class BiggerThanRightTwice {
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public static int biggerTwice(int[] arr) {
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if (arr.length < 2 || arr == null) {
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return 0;
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}
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return process(arr, 0, arr.length - 1);
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}
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private static int process(int[] arr, int l, int r) {
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if (l == r) {
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return 0;
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}
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int mid = l + ((r - l) >> 1);
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return process(arr, l, mid) + process(arr, mid + 1, r) + merge(arr, l, mid, r);
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}
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private static int merge(int[] arr, int l, int m, int r) {
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int res = 0;
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int R = m;
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for (int i = l; i <= m; i++) {
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while (R + 1 <= r && arr[i] > (arr[R + 1] << 1)) {
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R++;
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}
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res += R - m;
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}
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int[] help = new int[r - l + 1];
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int i = 0;
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int p1 = l;
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int p2 = m + 1;
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while (p1 <= m && p2 <= r) {
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help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
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}
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while (p1 <= m) {
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help[i++] = arr[p1++];
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}
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while (p2 <= r) {
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help[i++] = arr[p2++];
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}
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for (i = 0; i < help.length; i++) {
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arr[l + i] = help[i];
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}
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return res;
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}
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}
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class BiggerThanRightTwice1 {
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public static int biggerTwice(int[] arr) {
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if (arr.length < 2 || arr == null) {
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return 0;
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}
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return process(arr, 0, arr.length - 1);
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}
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private static int process(int[] arr, int l, int r) {
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if (l == r) {
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return 0;
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}
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int mid = l + ((r - l) >> 1);
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return process(arr, l, mid) + process(arr, mid + 1, r) + merge(arr, l, mid, r);
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}
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private static int merge(int[] arr, int l, int m, int r) {
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int res = 0;
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int windowR = m + 1;
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for (int i = l; i <= m; i++) {
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while (windowR <= r && arr[i] > (arr[windowR] << 1)) {
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windowR++;
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}
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res += windowR - m - 1;
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}
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int[] help = new int[r - l + 1];
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int p1 = l;
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int p2 = m + 1;
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int i = 0;
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while (p1 <= m && p2 <= r) {
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help[i++] = arr[p1] <= arr[p2] ? arr[p1++] : arr[p2++];
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}
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while(p1<=m){
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help[i++] = arr[p1++];
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}
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while (p2 <= r) {
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help[i++] = arr[p2++];
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}
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for (i = 0; i < help.length; i++) {
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arr[l + i] = help[i];
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}
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return res;
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}
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}
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class BiggerThanRightTwice2 {
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public static int biggerTwice(int[] arr) {
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if (arr.length < 2 || arr == null) {
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return 0;
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}
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return process(arr, 0, arr.length - 1);
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}
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private static int process(int[] arr, int l, int r) {
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if (l==r){
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return 0;
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}
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int m = l + ((r - l) >> 1);
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return process(arr, l, m) + process(arr, m + 1, r) + merge(arr, l, m, r);
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}
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private static int merge(int[] arr, int l, int m, int r) {
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int windowR = m + 1;
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int res = 0;
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for (int i = l; i <= m; i++) {
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while (windowR <= r && arr[i] > (arr[windowR] << 1)) {
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windowR++;
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}
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res += windowR - m - 1;
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}
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int[] help = new int[r - l + 1];
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int i = 0;
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int p1 = l;
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int p2 = m + 1;
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while (p1 <= m && p2 <= r) {
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help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
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}
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while (p1 <= m) {
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help[i++] = arr[p1++];
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}
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while (p2 <= r) {
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help[i++] = arr[p2++];
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}
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for (i = 0; i < help.length; i++) {
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arr[l + i] = help[i];
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}
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return res;
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}
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}
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class BiggerThanRightTwice3 {
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public static int biggerTwice(int[] arr) {
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if (arr.length < 2 || arr == null) {
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return 0;
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}
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return process(arr, 0, arr.length - 1);
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}
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private static int process(int[] arr, int l, int r) {
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if (l == r) {
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return 0;
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}
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int m = l + ((r - l) >> 1);
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return process(arr, l, m) + process(arr, m + 1, r) + merge(arr, l, m, r);
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}
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private static int merge(int[] arr, int l, int m, int r) {
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int res = 0;
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int windowR = m + 1;
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for (int i = l; i <= m; i++) {
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while (windowR <= r && arr[i] > (arr[windowR] << 1)) {
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windowR++;
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}
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res += windowR - m-1;
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}
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int p1 = l;
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int p2 = m + 1;
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int i = 0;
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int[] help = new int[r - l + 1];
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while (p1 <= m && p2 <= r) {
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help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
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}
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while (p1 <= m) {
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help[i++] = arr[p1++];
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}
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while (p2 <= r) {
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help[i++] = arr[p2++];
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}
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for (i = 0; i < help.length; i++) {
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arr[l + i] = help[i];
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}
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return res;
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}
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}
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class TestBiggerThanRightTwice {
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public static int biggerTwice(int[] arr) {
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int res = 0;
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for (int i = 0; i < arr.length; i++) {
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for (int j = i + 1; j < arr.length; j++) {
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if (arr[i] > arr[j] << 1) {
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res++;
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}
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}
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}
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return res;
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}
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}
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class Main{
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public static void main(String[] args){
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int testTime = 1000;
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int sizeMax = 10;
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int range = 60;
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System.out.println("start");
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for (int i = 0; i < testTime; i++) {
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int[] arr = generateRandomArray(sizeMax, range);
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int[] copyArray = copyArray(arr);
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int res = BiggerThanRightTwice3.biggerTwice(arr);
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int res1 = TestBiggerThanRightTwice.biggerTwice(copyArray);
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if (res != res1) {
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System.out.println("res : " + res + " " + " res1: " + res1);
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return;
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}
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}
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System.out.println("end");
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}
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public static int[] generateRandomArray(int sizeMax, int range) {
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int[] arr = new int[(int) (sizeMax * Math.random() + 1)];
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for (int i = 0; i < arr.length; i++) {
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arr[i] = (int) ((range * Math.random() - 1) - (range * Math.random() - 1));
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}
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return arr;
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}
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public static int[] copyArray(int[] arr) {
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int[] copyArr = new int[arr.length];
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for (int i = 0; i < arr.length; i++) {
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copyArr[i] = arr[i];
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}
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return copyArr;
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}
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}
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