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package class_2022_03_3_week;
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import java.util.Arrays;
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// 来自美团
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// 给定一个数组arr，你可以随意挑选其中的数字
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// 但是你挑选的数中，任何两个数a和b，必须Math.abs(a - b) > 1
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// 返回你最多能挑选几个数
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public class Code01_LongestUncontinuousSet {
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// 暴力方法
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// 为了验证
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public static int longestUncontinuous1(int[] arr) {
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if (arr == null || arr.length == 0) {
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return 0;
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}
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Arrays.sort(arr);
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return process1(arr, 0, new int[arr.length], 0);
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}
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public static int process1(int[] arr, int i, int[] path, int j) {
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if (i == arr.length) {
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for (int k = 1; k < j; k++) {
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if (path[k - 1] + 1 >= path[k]) {
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return 0;
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}
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}
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return j;
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} else {
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int p1 = process1(arr, i + 1, path, j);
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path[j] = arr[i];
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int p2 = process1(arr, i + 1, path, j + 1);
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return Math.max(p1, p2);
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}
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}
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// 最优解
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public static int longestUncontinuous2(int[] arr) {
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if (arr == null || arr.length == 0) {
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return 0;
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}
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Arrays.sort(arr);
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int n = arr.length;
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int size = 1;
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for (int i = 1; i < n; i++) {
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if (arr[i] != arr[size - 1]) {
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arr[size++] = arr[i];
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}
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}
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int[] dp = new int[size];
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dp[0] = 1;
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int ans = 1;
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for (int i = 1; i < size; i++) {
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dp[i] = 1;
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if (arr[i] - arr[i - 1] > 1) {
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dp[i] = 1 + dp[i - 1];
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}
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if (i - 2 >= 0 && arr[i] - arr[i - 2] > 1) {
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dp[i] = Math.max(dp[i], 1 + dp[i - 2]);
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}
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ans = Math.max(ans, dp[i]);
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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 int[] randomArray(int n, int v) {
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int[] arr = new int[n];
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for (int i = 0; i < n; i++) {
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arr[i] = (int) (Math.random() * v) - (int) (Math.random() * v);
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}
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return arr;
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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 len = 10;
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int value = 20;
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int testTime = 2000;
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System.out.println("测试开始");
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for (int i = 0; i < testTime; i++) {
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int n = (int) (Math.random() * len) + 1;
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int[] arr = randomArray(n, value);
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int ans1 = longestUncontinuous1(arr);
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int ans2 = longestUncontinuous2(arr);
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if (ans1 != ans2) {
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System.out.println("出错了!");
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for (int num : arr) {
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System.out.print(num + " ");
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}
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System.out.println();
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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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