Is there any way to find frequency of a number in a given range using segment tree? -


suppose, i've array [1, 2, 3, 5, 5, 6, 5, 5]

now, there can 2 kind of operation. 1 of them "update" operation , increase value in index 4[1 based indexing] x. other operation "query" operation, given range, suppose [4, 8](both inclusive) , value suppose 5. find frequency of value 5 in given range [4, 8]. in case, answer should 4.

how can "query" step using segment tree??

thanks in advance.

i have 2 solutions without using segment tree

first solution :

  • split each query freq(r,x)-freq(l-1,x)

  • iterate on input , store counts in array (or map if
    range big)

  • if there query on position, add/subtract count array should work in o(n + q) if elements small enough
    array or o(n + q log n) if need use map.

second solution : use mo's algorithm solving problem time complexity o((n + q) * sqrt(n) * f).


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