programming-examples/c++/Basic/FenwickTreeOnMap.cpp

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2019-11-18 14:44:36 +01:00
#include <iostream>
#include <map>
using namespace std;
const int n = 2000000000;
void add(map<int, int> &t, int i, int value) {
for (; i < n; i |= i + 1)
t[i] += value;
}
// sum[0,i]
int sum(map<int, int> &t, int i) {
int res = 0;
for (; i >= 0; i = (i & (i + 1)) - 1)
if (t.count(i)) res += t[i];
return res;
}
// Usage example
int main() {
map<int, int> t;
add(t, 0, 4);
add(t, 1, 5);
add(t, 2, 5);
add(t, 2, 5);
cout << (4 == sum(t, 0)) << endl;
cout << (19 == sum(t, 2)) << endl;
cout << (19 == sum(t, 1000000000)) << endl;
}