Merge pull request #22 from raunak96/master

Added Binary Indexed Tree

Author: iam-hitesh

data_structure/BIT_subarrays_sum_in_given_range.cpp

@@ -0,0 +1,55 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define N 500000
+pair<long long int,int> a[N+1],c[N+1];
+long long int b;
+int bit[N+1];
+void update(int ind,int n)
+{
+ while(ind<=n)
+ {
+ bit[ind]++;
+ ind+=ind&(-ind);
+ }
+}
+long long int que(int ind)
+{
+ long long int ans=0;
+ while(ind>0)
+ {
+ ans+=bit[ind];
+ ind-=ind&(-ind);
+ }
+ return ans;
+}
+int main()
+{
+ios_base::sync_with_stdio(false);
+ cin.tie(0);
+ int n,q;
+long long int cnt,l,r;
+cin>>n>>q;
+for(int i=1;i<=n;i++)
+ cin>>b,a[i].first+=a[i-1].first+b,a[i].second=i,c[i]=a[i];
+sort(c+1,c+n+1);
+for(int i=1;i<=n;i++)
+ a[c[i].second].second=i;
+while(q--)
+{
+ cnt=0;
+ cin>>l>>r;
+ for(int i=1;i<=n;i++)
+ {
+ int h=upper_bound(c+1,c+n+1,make_pair(a[i].first-l,INT_MAX))-c;
+ int lo=lower_bound(c+1,c+n+1,make_pair(a[i].first-r,INT_MIN))-c;
+ if(a[i].first>=l && a[i].first<=r)
+ cnt+=1;
+ cnt+=que(h-1)-que(lo-1);
+ update(a[i].second,n);
+ }
+ cout<<cnt<<endl;
+ for(int i=1;i<=n;i++)
+ bit[i]=0;
+}
+return 0;
+}

data_structure/invcnt_BIT.cpp

@@ -0,0 +1,48 @@
+#include<bits/stdc++.h>
+using namespace std;
+#define siz 200000
+long long int bit[siz+1];
+pair<int,int> a[siz+1];
+long long int que(int x)
+{
+ long long int ans=0;
+ while(x>0)
+ {
+ ans+=bit[x];
+ x-=(x&-x);
+ }
+ return ans;
+}
+void update(int ind,int n)
+{
+ while(ind<=n)
+ {
+ bit[ind]++;
+ ind+=(ind&-ind);
+ }
+}
+int main()
+{
+ int t,n,r,maxi;
+ long long int cnt;
+ scanf("%d",&t);
+ while(t--)
+ {
+ cnt=0;
+ scanf("%d",&n);
+ for(int i=1;i<=n;i++)
+ {
+ scanf("%d",&a[i].first);
+ a[i].second=i;
+ }
+ sort(a+1,a+n+1);
+ for(int i=1;i<=n;i++)
+ {
+ cnt+=que(n)-que(a[i].second);
+ update(a[i].second,n);
+ }
+ printf("%lld\n",cnt);
+ for(int i=1;i<=n;i++)
+ bit[i]=0;
+ }
+}