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package class_2022_04_1_week;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.PriorityQueue;
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// 来自Amazon
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// 给定一个数组arr，含有n个数字，可能有正、有负、有0
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// 给定一个正数k
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// 返回所有子序列中，累加和最大的前k个子序列累加和
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// 假设K不大，怎么算最快？
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public class Code07_TopMaxSubsquenceSum {
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public static int[] topMaxSum1(int[] arr, int k) {
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ArrayList<Integer> allAns = new ArrayList<>();
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process(arr, 0, 0, allAns);
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allAns.sort((a, b) -> a.compareTo(b));
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int[] ans = new int[k];
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for (int i = allAns.size() - 1, j = 0; j < k; i--, j++) {
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ans[j] = allAns.get(i);
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}
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return ans;
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}
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public static void process(int[] arr, int index, int sum, ArrayList<Integer> ans) {
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if (index == arr.length) {
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ans.add(sum);
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} else {
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process(arr, index + 1, sum, ans);
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process(arr, index + 1, sum + arr[index], ans);
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}
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}
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public static int[] topMaxSum2(int[] arr, int k) {
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int sum = 0;
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for (int i = 0; i < arr.length; i++) {
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if (arr[i] >= 0) {
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sum += arr[i];
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} else {
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arr[i] = -arr[i];
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}
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}
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int[] ans = topMinSum(arr, k);
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for (int i = 0; i < ans.length; i++) {
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ans[i] = sum - ans[i];
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}
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return ans;
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}
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public static int[] topMinSum(int[] arr, int k) {
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Arrays.sort(arr);
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PriorityQueue<int[]> heap = new PriorityQueue<>((a, b) -> a[1] - b[1]);
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heap.add(new int[] { 0, arr[0] });
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int[] ans = new int[k];
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for (int i = 1; i < k; i++) {
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int[] cur = heap.poll();
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int last = cur[0];
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int sum = cur[1];
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ans[i] = sum;
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if (last + 1 < arr.length) {
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heap.add(new int[] { last + 1, sum - arr[last] + arr[last + 1] });
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heap.add(new int[] { last + 1, sum + arr[last + 1] });
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}
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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 len, int value) {
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int[] arr = new int[len];
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for (int i = 0; i < len; i++) {
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arr[i] = (int) (Math.random() * value) + 1;
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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 boolean equals(int[] ans1, int[] ans2) {
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if (ans1.length != ans2.length) {
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return false;
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}
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for (int i = 0; i < ans1.length; i++) {
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if (ans1[i] != ans2[i]) {
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return false;
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}
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}
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return true;
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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 = 10;
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int v = 40;
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int testTime = 5000;
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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 len = (int) (Math.random() * n) + 1;
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int[] arr = randomArray(len, v);
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int k = (int) (Math.random() * ((1 << len) - 1)) + 1;
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int[] ans1 = topMaxSum1(arr, k);
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int[] ans2 = topMaxSum2(arr, k);
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if (!equals(ans1, ans2)) {
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System.out.println("出错了！");
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System.out.print("arr : ");
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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("k : " + k);
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for (int num : ans1) {
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System.out.print(num + " ");
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}
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System.out.println();
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for (int num : ans2) {
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System.out.print(num + " ");
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}
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System.out.println();
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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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