79 lines
2.1 KiB
Java
79 lines
2.1 KiB
Java
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import java.util.*;
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// Solution of http://www.spoj.com/problems/DQUERY/en/
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public class MosAlgorithm2 {
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static int solveSlow(int[] cnt, int[] a, int haveLeft, int haveRight, int needLeft, int needRight) {
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int res = 0;
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for (int i = haveRight + 1; i <= needRight; ++i) {
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res += cnt[a[i]] == 0 ? 1 : 0;
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++cnt[a[i]];
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}
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for (int i = haveLeft; i < needLeft; ++i) {
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res += cnt[a[i]] == 1 ? -1 : 0;
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--cnt[a[i]];
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}
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for (int i = haveRight + 1; i <= needRight; ++i) {
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--cnt[a[i]];
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}
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for (int i = haveLeft; i < needLeft; ++i) {
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++cnt[a[i]];
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}
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return res;
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}
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static int[] solve(int[] a, int[][] queries) {
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int n = a.length;
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Map<Integer, Integer> m = new HashMap<>();
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int id = 0;
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for (int i = 0; i < n; i++) {
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if (!m.containsKey(a[i]))
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m.put(a[i], id++);
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a[i] = m.get(a[i]);
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}
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int blockSize = (int) Math.sqrt(n);
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int blocks = (n + blockSize - 1) / blockSize;
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int[][] head = new int[blocks][blocks];
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for (int i = 0; i < blocks; i++)
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Arrays.fill(head[i], -1);
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int q = queries.length;
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int[] left = new int[q];
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int[] right = new int[q];
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int[] next = new int[q];
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for (int i = 0; i < q; i++) {
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left[i] = queries[i][0];
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right[i] = queries[i][1];
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int lb = left[i] / blockSize;
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int rb = right[i] / blockSize;
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next[i] = head[lb][rb];
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head[lb][rb] = i;
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}
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int[] res = new int[q];
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for (int leftBlock = 0; leftBlock < blocks; leftBlock++) {
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int[] cnt = new int[id];
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int curAnswer = 0;
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for (int rightBlock = leftBlock; rightBlock < blocks; rightBlock++) {
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for (int i = head[leftBlock][rightBlock]; i >= 0; i = next[i]) {
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res[i] = curAnswer
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+ solveSlow(cnt, a, leftBlock * blockSize, rightBlock * blockSize - 1, left[i], right[i]);
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}
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if (rightBlock + 1 < blocks) {
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for (int i = 0; i < blockSize; i++) {
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int cur = a[rightBlock * blockSize + i];
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curAnswer += cnt[cur] == 0 ? 1 : 0;
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++cnt[cur];
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}
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}
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}
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}
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return res;
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}
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public static void main(String[] args) {
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int[] a = {1, 2, 3, 4};
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int[][] queries = {{3, 3}};
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int[] res = solve(a, queries);
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System.out.println(Arrays.toString(res));
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}
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}
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