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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);
 */




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