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Create Fenwick Tree-Range Sum Queries.cpp #37

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31 changes: 31 additions & 0 deletions Algorithms/Fenwick Tree-Range Sum Queries.cpp
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Original file line number Diff line number Diff line change
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struct FenwickTree {
vector<int> bit; // binary indexed tree
int n;

FenwickTree(int n) {
this->n = n;
bit.assign(n, 0);
}

FenwickTree(vector<int> a) : FenwickTree(a.size()) {
for (size_t i = 0; i < a.size(); i++)
add(i, a[i]);
}

int sum(int r) {
int ret = 0;
for (; r >= 0; r = (r & (r + 1)) - 1)
ret += bit[r];
return ret;
}

int sum(int l, int r) {
return sum(r) - sum(l - 1);
}

void add(int idx, int delta) {
for (; idx < n; idx = idx | (idx + 1))
bit[idx] += delta;
}
};