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package class_2022_02_3_week;
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import java.util.Arrays;
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// 来自微软
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// 给定一个数组arr，一个正数num，一个正数k
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// 可以把arr中的某些数字拿出来组成一组，要求该组中的最大值减去最小值<=num
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// 且该组数字的个数一定要正好等于k
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// 每个数字只能选择进某一组，不能进多个组
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// 返回arr中最多有多少组
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public class Code04_MaxTeamNumber {
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// 对数器方法
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public static int maxTeams1(int[] arr, int num, int k) {
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Arrays.sort(arr);
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return process1(arr, 0, new int[arr.length], 0, num, k);
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}
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public static int process1(int[] arr, int index, int[] path, int size, int num, int k) {
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if (index == arr.length) {
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if (size % k != 0) {
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return 0;
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} else {
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for (int start = 0; start < size; start += k) {
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if (path[start + k - 1] - path[start] > num) {
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return 0;
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}
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}
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return size / k;
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}
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} else {
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int p1 = process1(arr, index + 1, path, size, num, k);
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path[size] = arr[index];
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int p2 = process1(arr, index + 1, path, size + 1, num, k);
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return Math.max(p1, p2);
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}
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}
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// 正式方法
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// 时间复杂度O(N * logN)
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public static int maxTeams2(int[] arr, int num, int k) {
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int n = arr.length;
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if (k > n) {
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return 0;
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}
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Arrays.sort(arr);
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int[] dp = new int[n];
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dp[k - 1] = arr[k - 1] - arr[0] <= num ? 1 : 0;
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for (int i = k; i < n; i++) {
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int p1 = dp[i - 1];
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int p2 = (arr[i] - arr[i - k + 1] <= num ? 1 : 0) + dp[i - k];
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dp[i] = Math.max(p1, p2);
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}
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return dp[n - 1];
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}
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// 为了测试
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public static int[] randomArray(int len, int value) {
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int[] ans = new int[len];
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for (int i = 0; i < len; i++) {
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ans[i] = (int) (Math.random() * value);
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}
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return ans;
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}
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// 为了测试
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public static void main(String[] args) {
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int n = 18;
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int v = 50;
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int testTimes = 20000;
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System.out.println("测试开始");
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for (int i = 0; i < testTimes; i++) {
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int len = (int) (Math.random() * n) + 1;
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int[] arr = randomArray(len, v);
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int num = (int) (Math.random() * v) + 1;
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int k = (int) (Math.random() * len) + 1;
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int ans1 = maxTeams1(arr, num, k);
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int ans2 = maxTeams2(arr, num, k);
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if (ans1 != ans2) {
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for (int number : arr) {
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System.out.print(number + " ");
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}
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System.out.println();
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System.out.println("num : " + num);
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System.out.println("k : " + k);
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System.out.println(ans1);
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System.out.println(ans2);
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break;
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}
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}
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System.out.println("测试结束");
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}
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}
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