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Update bit.cpp

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John Law
2019-10-09 00:01:36 +08:00
committed by GitHub
parent 1b3521d861
commit 883d9dc3a4
1 changed files with 64 additions and 54 deletions
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118
Range queries/bit.cpp
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@@ -1,66 +1,76 @@
// Binary Indexed Tree.
#include<bits/stdc++.h>
using namespace std;
class Bit{
int n;
vector<int> bit;
inline int offset(int x){ return (x & (-x)); }
public:
Bit(vector<int>& arr){
n = arr.size();
bit.assign(n+1,0);
for(int i=0; i<n; ++i){
update(i,arr[i]);
}
}
Bit(int x){
n = x;
bit.assign(n+1,0);
}
void update(int id, int val){
// Add val at id
id++;
while( id <= n ){
bit[id] += val;
id += offset(id);
class Bit
{
int n;
vector < int > bit;
inline int offset(int x)
{
return (x & (-x));
}
}
int sum(int id){
// Get prefix sum upto id.
id++;
int res = 0;
while( id > 0 ){
res += bit[id];
id -= offset(id);
public:
Bit(vector < int > & arr)
{
n = arr.size();
bit.assign(n + 1, 0);
for (int i = 0; i < n; ++i)
{
update(i, arr[i]);
}
}
Bit(int x)
{
n = x;
bit.assign(n + 1, 0);
}
return res;
}
int sum_range(int l, int r){
return sum(r) - sum(l-1);
}
void update(int id, int val)
{
// Add val at id
id++;
while (id <= n)
{
bit[id] += val;
id += offset(id);
}
}
int sum(int id)
{
// Get prefix sum upto id.
id++;
int res = 0;
while (id > 0)
{
res += bit[id];
id -= offset(id);
}
return res;
}
int sum_range(int l, int r)
{
return sum(r) - sum(l - 1);
}
};
int main()
{
int n = 5;
vector <int> arr = { 1, 2, 3, 4, 5 };
Bit x(arr);
int main(){
int n = 5;
vector<int> arr = {1,2,3,4,5};
Bit x(arr);
assert(x.sum_range(0,0) == 1);
assert(x.sum_range(0,1) == 3);
assert(x.sum_range(0,2) == 6);
x.update(0,6);
assert(x.sum_range(0,0) == 6);
assert(x.sum_range(0,1) == 8);
assert(x.sum_range(0,2) == 11);
assert(x.sum_range(0, 0) == 1);
assert(x.sum_range(0, 1) == 3);
assert(x.sum_range(0, 2) == 6);
x.update(0, 6);
assert(x.sum_range(0, 0) == 6);
assert(x.sum_range(0, 1) == 8);
assert(x.sum_range(0, 2) == 11);
return 0;
}