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package class_2022_08_1_week;
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import java.util.ArrayList;
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// 设计一个数据结构，有效地找到给定子数组的 多数元素 。
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// 子数组的 多数元素 是在子数组中出现 threshold 次数或次数以上的元素。
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// 实现 MajorityChecker 类:
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// MajorityChecker(int[] arr)
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// 会用给定的数组 arr 对 MajorityChecker 初始化。
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// int query(int left, int right, int threshold)
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// 返回子数组中的元素 arr[left...right] 至少出现 threshold 次数，
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// 如果不存在这样的元素则返回 -1。
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// 为了让同学们听懂这个题
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// 才安排的水王问题重讲
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// 测试链接 : https://leetcode.cn/problems/online-majority-element-in-subarray/
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public class Code03_OnlineMajorityElementInSubarray {
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class MajorityChecker {
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SegmentTree st;
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CountQuicker cq;
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public MajorityChecker(int[] arr) {
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st = new SegmentTree(arr);
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cq = new CountQuicker(arr);
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}
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public int query(int left, int right, int threshold) {
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int candidate = st.query(left, right);
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return cq.realTimes(left, right, candidate) >= threshold ? candidate : -1;
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}
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class SegmentTree {
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int n;
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int[] candidate;
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int[] hp;
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public SegmentTree(int[] arr) {
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n = arr.length;
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candidate = new int[(n + 1) << 2];
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hp = new int[(n + 1) << 2];
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build(arr, 1, n, 1);
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}
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private void build(int[] arr, int l, int r, int rt) {
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if (l == r) {
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candidate[rt] = arr[l - 1];
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hp[rt] = 1;
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} else {
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int m = (l + r) >> 1;
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build(arr, l, m, rt << 1);
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build(arr, m + 1, r, rt << 1 | 1);
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int lc = candidate[rt << 1];
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int rc = candidate[rt << 1 | 1];
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int lh = hp[rt << 1];
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int rh = hp[rt << 1 | 1];
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if (lc == rc) {
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candidate[rt] = lc;
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hp[rt] = lh + rh;
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} else {
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candidate[rt] = lh >= rh ? lc : rc;
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hp[rt] = Math.abs(lh - rh);
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}
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}
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}
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public int query(int left, int right) {
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return query(left + 1, right + 1, 1, n, 1)[0];
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}
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private int[] query(int L, int R, int l, int r, int rt) {
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if (L <= l && r <= R) {
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return new int[] { candidate[rt], hp[rt] };
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}
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int m = (l + r) >> 1;
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if (R <= m) {
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return query(L, R, l, m, rt << 1);
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} else if (L > m) {
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return query(L, R, m + 1, r, rt << 1 | 1);
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} else {
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int[] ansl = query(L, R, l, m, rt << 1);
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int[] ansr = query(L, R, m + 1, r, rt << 1 | 1);
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if (ansl[0] == ansr[0]) {
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ansl[1] += ansr[1];
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return ansl;
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} else {
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if (ansl[1] >= ansr[1]) {
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ansl[1] -= ansr[1];
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return ansl;
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} else {
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ansr[1] -= ansl[1];
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return ansr;
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}
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}
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}
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}
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}
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class CountQuicker {
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// v : i1 i14 i15
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ArrayList<ArrayList<Integer>> cnt;
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public CountQuicker(int[] arr) {
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cnt = new ArrayList<>();
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int max = 0;
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for (int num : arr) {
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max = Math.max(max, num);
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}
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for (int i = 0; i <= max; i++) {
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cnt.add(new ArrayList<>());
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}
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for (int i = 0; i < arr.length; i++) {
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cnt.get(arr[i]).add(i);
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}
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}
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public int realTimes(int left, int right, int num) {
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ArrayList<Integer> indies = cnt.get(num);
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return size(indies, right) - size(indies, left - 1);
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}
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private int size(ArrayList<Integer> indies, int index) {
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int l = 0;
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int r = indies.size() - 1;
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int m = 0;
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int ans = -1;
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while (l <= r) {
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m = (l + r) / 2;
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if (indies.get(m) <= index) {
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ans = m;
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l = m + 1;
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} else {
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r = m - 1;
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}
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}
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return ans + 1;
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}
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}
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}
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}
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