55 lines
1.4 KiB
Java
55 lines
1.4 KiB
Java
|
import java.util.Arrays;
|
||
|
|
|
||
|
|
// https://www.hackerearth.com/notes/mos-algorithm/
|
||
|
|
// Solution of http://www.spoj.com/problems/DQUERY/en/
|
||
|
|
public class MosAlgorithm {
|
||
|
|
|
||
|
|
public static class Query {
|
||
|
|
int index;
|
||
|
|
int a;
|
||
|
|
int b;
|
||
|
|
|
||
|
|
public Query(int a, int b) {
|
||
|
|
this.a = a;
|
||
|
|
this.b = b;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
static int add(int[] a, int[] cnt, int i) {
|
||
|
|
return ++cnt[a[i]] == 1 ? 1 : 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
static int remove(int[] a, int[] cnt, int i) {
|
||
|
|
return --cnt[a[i]] == 0 ? -1 : 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
public static int[] processQueries(int[] a, Query[] queries) {
|
||
|
|
for (int i = 0; i < queries.length; i++) queries[i].index = i;
|
||
|
|
int sqrtn = (int) Math.sqrt(a.length);
|
||
|
|
Arrays.sort(queries, (q1, q2) -> {
|
||
|
|
int cmp = Integer.compare(q1.a / sqrtn, q2.a / sqrtn);
|
||
|
|
return cmp != 0 ? cmp : Integer.compare(q1.b, q2.b);
|
||
|
|
});
|
||
|
|
int[] cnt = new int[1000_002];
|
||
|
|
int[] res = new int[queries.length];
|
||
|
|
int L = 1;
|
||
|
|
int R = 0;
|
||
|
|
int cur = 0;
|
||
|
|
for (Query query : queries) {
|
||
|
|
while (L < query.a) cur += remove(a, cnt, L++);
|
||
|
|
while (L > query.a) cur += add(a, cnt, --L);
|
||
|
|
while (R < query.b) cur += add(a, cnt, ++R);
|
||
|
|
while (R > query.b) cur += remove(a, cnt, R--);
|
||
|
|
res[query.index] = cur;
|
||
|
|
}
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
|
||
|
|
public static void main(String[] args) {
|
||
|
|
int[] a = {1, 3, 3, 4};
|
||
|
|
Query[] queries = {new Query(0, 3), new Query(1, 3), new Query(2, 3), new Query(3, 3)};
|
||
|
|
int[] res = processQueries(a, queries);
|
||
|
|
System.out.println(Arrays.toString(res));
|
||
|
|
}
|
||
|
|
}
|