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Java-based LeetCode algorithm problem solutions, regularly updated
package g2001_2100.s2080_range_frequency_queries;
// #Medium #Array #Hash_Table #Binary_Search #Design #Segment_Tree
// #2022_03_31_Time_140_ms_(97.86%)_Space_135.9_MB_(93.16%)
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* 2080 - Range Frequency Queries\.
*
* Medium
*
* Design a data structure to find the **frequency** of a given value in a given subarray.
*
* The **frequency** of a value in a subarray is the number of occurrences of that value in the subarray.
*
* Implement the `RangeFreqQuery` class:
*
* * `RangeFreqQuery(int[] arr)` Constructs an instance of the class with the given **0-indexed** integer array `arr`.
* * `int query(int left, int right, int value)` Returns the **frequency** of `value` in the subarray `arr[left...right]`.
*
* A **subarray** is a contiguous sequence of elements within an array. `arr[left...right]` denotes the subarray that contains the elements of `nums` between indices `left` and `right` ( **inclusive** ).
*
* **Example 1:**
*
* **Input**
*
* ["RangeFreqQuery", "query", "query"]
* [[[12, 33, 4, 56, 22, 2, 34, 33, 22, 12, 34, 56]], [1, 2, 4], [0, 11, 33]]
*
* **Output:** [null, 1, 2]
*
* **Explanation:**
*
* RangeFreqQuery rangeFreqQuery = new RangeFreqQuery([12, 33, 4, 56, 22, 2, 34, 33, 22, 12, 34, 56]);
* rangeFreqQuery.query(1, 2, 4); // return 1. The value 4 occurs 1 time in the subarray [33, 4]
* rangeFreqQuery.query(0, 11, 33); // return 2. The value 33 occurs 2 times in the whole array.
*
* **Constraints:**
*
* * 1 <= arr.length <= 105
* * 1 <= arr[i], value <= 104
* * `0 <= left <= right < arr.length`
* * At most 105
calls will be made to `query`
**/
public class RangeFreqQuery {
private Map> map;
public RangeFreqQuery(int[] arr) {
map = new HashMap<>();
for (int i = 0; i < arr.length; i++) {
if (!map.containsKey(arr[i])) {
map.put(arr[i], new ArrayList<>());
}
map.get(arr[i]).add(i);
}
}
public int query(int left, int right, int value) {
if (!map.containsKey(value)) {
return 0;
}
List list = map.get(value);
int s = Collections.binarySearch(list, left);
int e = Collections.binarySearch(list, right);
if (s < 0) {
s = (s + 1) * -1;
}
if (e < 0) {
e = (e + 2) * -1;
}
return e - s + 1;
}
}
/*
* Your RangeFreqQuery object will be instantiated and called as such:
* RangeFreqQuery obj = new RangeFreqQuery(arr);
* int param_1 = obj.query(left,right,value);
*/