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// 2080. Range Frequency Queries
#include "leetcode.h"
/*
* 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 occurences
* of that value in the subarray. implement the 'RangeFreqQuery' class:
* 'rangeFreqQueryCreate(int[] arr)' constructs an instance of the class with
* the given 0-indexed integer array 'arr'. 'int RangeFreqQuery(int left, int
* right, int val)' returns the frequency of 'val' in the subarray 'arr[left ...
* right]'. a subarray is contiguous sequence of elements within an array.
* 'arr[left ... right]' denotes the subarray that contains the elements of
* 'nums' between indices 'left' and 'right' inclusively
*/
typedef struct {
int *a;
int size;
} RangeFreqQuery;
int cmp(const void *a, const void *b) { return (*(int *)a - *(int *)b); }
RangeFreqQuery *rangeFreqQueryCreate(int *arr, int arrSize) {
RangeFreqQuery *obj = (RangeFreqQuery *)calloc(1, sizeof(RangeFreqQuery));
obj->size = arrSize + 1;
obj->a = (int *)calloc(obj->size, sizeof(int));
for (int i = 0; i < arrSize; i++)
obj->a[i] = arr[i] << 17 | i;
obj->a[arrSize] = 10001 << 17;
qsort(obj->a, obj->size - 1, sizeof(int), cmp);
return obj;
}
int bsearch1(int *a, int size, int target) {
int l = 0, r = size - 1, m;
while (l < r) {
m = l + ((r - l) >> 1);
if (a[m] < target)
l = m + 1;
else
r = m;
}
return l;
}
int bsearch2(int *a, int size, int target) {
int l = 0, r = size - 1, m;
while (l < r) {
m = l + ((r - l) >> 1);
if (a[m] <= target)
l = m + 1;
else
r = m;
}
return l;
}
int rangeFreqQueryQuery(RangeFreqQuery *obj, int left, int right, int value) {
int l = bsearch1(obj->a, obj->size, value << 17 | left);
int r = bsearch2(obj->a, obj->size, value << 17 | right);
return r - l;
}
void rangeFreqQueryFree(RangeFreqQuery *obj) {
free(obj->a);
free(obj);
}
int main() {
int arr[] = {12, 33, 4, 56, 22, 2, 34, 33, 22, 12, 34, 56};
RangeFreqQuery *obj = rangeFreqQueryCreate(arr, ARRAY_SIZE(arr));
printf("%d\n", rangeFreqQueryQuery(obj, 1, 2, 4)); // expect: 1
printf("%d\n", rangeFreqQueryQuery(obj, 0, 11, 33)); // expect: 2
rangeFreqQueryFree(obj);
}
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