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package class_2022_08_4_week;
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// 来自微软
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// 给定一个字符串s，只含有0~9这些字符
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// 你可以使用来自s中的数字，目的是拼出一个最大的回文数
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// 使用数字的个数，不能超过s里含有的个数
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// 比如 :
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// 39878，能拼出的最大回文数是 : 898
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// 00900，能拼出的最大回文数是 : 9
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// 54321，能拼出的最大回文数是 : 5
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// 最终的结果以字符串形式返回
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// str的长度为N，1 <= N <= 100000
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// 测试链接 : https://leetcode.cn/problems/largest-palindromic-number/
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import java.util.Comparator;
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import java.util.HashMap;
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import java.util.PriorityQueue;
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public class Code04_MaxPalindromeNumber {
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public static String largestPalindromic(String s) {
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if (s == null || s.equals("")) {
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return "";
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}
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HashMap<Integer, Integer> map = new HashMap<>();
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int n = s.length();
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for (int i = 0; i < n; i++) {
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int number = s.charAt(i) - '0';
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map.put(number, map.getOrDefault(number, 0) + 1);
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}
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PriorityQueue<Record> heap = new PriorityQueue<>(new RecordComparator());
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for (int key : map.keySet()) {
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heap.add(new Record(key, map.get(key)));
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}
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Record top = heap.poll();
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if (top.times == 1) {
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return String.valueOf(top.number);
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} else if (top.number == 0) {
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return String.valueOf(heap.isEmpty() ? 0 : heap.peek().number);
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} else {
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StringBuilder left = new StringBuilder();
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left.append(top.number);
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top.times -= 2;
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if (top.times > 0) {
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heap.add(top);
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}
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while (!heap.isEmpty() && heap.peek().times > 1) {
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top = heap.poll();
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left.append(top.number);
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top.times -= 2;
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if (top.times > 0) {
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heap.add(top);
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}
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}
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StringBuilder ans = new StringBuilder();
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for (int i = 0; i < left.length(); i++) {
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ans.append(left.charAt(i));
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}
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if (!heap.isEmpty()) {
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ans.append(heap.peek().number);
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}
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for (int i = left.length() - 1; i >= 0; i--) {
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ans.append(left.charAt(i));
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}
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return ans.toString();
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}
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}
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public static class Record {
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public int number;
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public int times;
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public Record(int n, int t) {
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number = n;
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times = t;
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}
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}
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public static class RecordComparator implements Comparator<Record> {
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@Override
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public int compare(Record o1, Record o2) {
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if (o1.times == 1 && o2.times > 1) {
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return 1;
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}
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if (o1.times > 1 && o2.times == 1) {
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return -1;
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}
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return o2.number - o1.number;
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}
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}
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}
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