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2080. Range Frequency Queries

Description

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

Solutions

  • class RangeFreqQuery {
        private Map<Integer, List<Integer>> mp = new HashMap<>();
    
        public RangeFreqQuery(int[] arr) {
            for (int i = 0; i < arr.length; ++i) {
                mp.computeIfAbsent(arr[i], k -> new ArrayList<>()).add(i);
            }
        }
    
        public int query(int left, int right, int value) {
            if (!mp.containsKey(value)) {
                return 0;
            }
            List<Integer> arr = mp.get(value);
            int l = search(arr, left - 1);
            int r = search(arr, right);
            return r - l;
        }
    
        private int search(List<Integer> arr, int val) {
            int left = 0, right = arr.size();
            while (left < right) {
                int mid = (left + right) >> 1;
                if (arr.get(mid) > val) {
                    right = mid;
                } else {
                    left = mid + 1;
                }
            }
            return left;
        }
    }
    
    /**
     * Your RangeFreqQuery object will be instantiated and called as such:
     * RangeFreqQuery obj = new RangeFreqQuery(arr);
     * int param_1 = obj.query(left,right,value);
     */
    
  • class RangeFreqQuery {
    public:
        unordered_map<int, vector<int>> mp;
        RangeFreqQuery(vector<int>& arr) {
            for (int i = 0; i < arr.size(); ++i)
                mp[arr[i]].push_back(i);
        }
    
        int query(int left, int right, int value) {
            if (!mp.count(value)) return 0;
            auto& arr = mp[value];
            auto l = upper_bound(arr.begin(), arr.end(), left - 1);
            auto r = upper_bound(arr.begin(), arr.end(), right);
            return r - l;
        }
    };
    
    /**
     * Your RangeFreqQuery object will be instantiated and called as such:
     * RangeFreqQuery* obj = new RangeFreqQuery(arr);
     * int param_1 = obj->query(left,right,value);
     */
    
  • class RangeFreqQuery:
        def __init__(self, arr: List[int]):
            self.mp = defaultdict(list)
            for i, x in enumerate(arr):
                self.mp[x].append(i)
    
        def query(self, left: int, right: int, value: int) -> int:
            if value not in self.mp:
                return 0
            arr = self.mp[value]
            l, r = bisect_right(arr, left - 1), bisect_right(arr, right)
            return r - l
    
    
    # Your RangeFreqQuery object will be instantiated and called as such:
    # obj = RangeFreqQuery(arr)
    # param_1 = obj.query(left,right,value)
    
    
  • type RangeFreqQuery struct {
    	mp map[int][]int
    }
    
    func Constructor(arr []int) RangeFreqQuery {
    	mp := make(map[int][]int)
    	for i, v := range arr {
    		mp[v] = append(mp[v], i)
    	}
    	return RangeFreqQuery{mp}
    }
    
    func (this *RangeFreqQuery) Query(left int, right int, value int) int {
    	arr := this.mp[value]
    	l := sort.SearchInts(arr, left)
    	r := sort.SearchInts(arr, right+1)
    	return r - l
    }
    
    /**
     * Your RangeFreqQuery object will be instantiated and called as such:
     * obj := Constructor(arr);
     * param_1 := obj.Query(left,right,value);
     */
    
  • class RangeFreqQuery {
        private g: Map<number, number[]> = new Map();
    
        constructor(arr: number[]) {
            for (let i = 0; i < arr.length; ++i) {
                if (!this.g.has(arr[i])) {
                    this.g.set(arr[i], []);
                }
                this.g.get(arr[i])!.push(i);
            }
        }
    
        query(left: number, right: number, value: number): number {
            const idx = this.g.get(value);
            if (!idx) {
                return 0;
            }
            const search = (x: number): number => {
                let [l, r] = [0, idx.length];
                while (l < r) {
                    const mid = (l + r) >> 1;
                    if (idx[mid] >= x) {
                        r = mid;
                    } else {
                        l = mid + 1;
                    }
                }
                return l;
            };
            const l = search(left);
            const r = search(right + 1);
            return r - l;
        }
    }
    
    /**
     * Your RangeFreqQuery object will be instantiated and called as such:
     * var obj = new RangeFreqQuery(arr)
     * var param_1 = obj.query(left,right,value)
     */
    
    

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