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$ curl repovive.com/roadmaps/data-structures/advanced-trees/subtree-queries-implementation

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$ curl repovive.com/roadmaps/data-structures/advanced-trees/subtree-queries-implementation

Repovive

Subtree Queries - Implementation - Advanced Trees | Data Structures | Repovive

Repovive.

Data Structures19 sections · 729 units49h total

Open in Course

Subtree Queries - Implementation

Complete solution

Here's the solution:

function solve(tree, values, queries)
    eulerTour(root)

    // Build Fenwick tree on tour
    arr := array of size n
    for each node v
        arr[tin[v]] := values[v]
    buildFenwick(arr)

    for each query
        if query is update(u, newVal) then
            diff := newVal - values[u]
            values[u] := newVal
            fenwickUpdate(tin[u], diff)
        else // query is subtreeSum(u)
            print fenwickQuery(tout[u]) - fenwickQuery(tin[u] - 1)

Time: $O((n + q) \log n)$ . Simple and efficient.