Created
December 19, 2014 16:35
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Segment Tree for range add and range sum
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#pragma once | |
#include <vector> | |
#include <algorithm> | |
template<class T> | |
class segtree { | |
public: | |
struct node { T all; T part; }; | |
explicit segtree(size_t N=1, T init=0) | |
: _init(init), _N(N), _tree(2*N-1,{init,init}) {} | |
void add(size_t i, size_t j, T data) { | |
_add(i,j,data,0,0,_N); | |
} | |
T sum(size_t i, size_t j) { | |
return _sum(i,j,0,0,_N); | |
} | |
private: | |
void _add(size_t i, size_t j, T data, size_t k, size_t l, size_t r) { | |
if(j <= l || r <= i) return; | |
if(i <= l && r <= j) { | |
_tree[k].all += data; | |
} else { | |
_tree[k].part += data*(std::min(j,r)-std::max(i,l)); | |
_add(i,j,data,k*2+1,l,(l+r)/2); | |
_add(i,j,data,k*2+2,(l+r)/2,r); | |
} | |
} | |
T _sum(size_t i, size_t j, size_t k, size_t l, size_t r) { | |
if(j <= l || r <= i) return _init; | |
if(i <= l && r <= j) { | |
return _tree[k].part + _tree[k].all*(r-l); | |
} else { | |
const T vleft = _sum(i,j,k*2+1,l,(l+r)/2); | |
const T vright = _sum(i,j,k*2+2,(l+r)/2,r); | |
return _tree[k].all*(std::min(j,r)-std::max(i,l)) + vleft + vright; | |
} | |
} | |
private: | |
T _init; | |
size_t _N; | |
std::vector<node> _tree; | |
}; |
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