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Merge pull request fnplus#604 from krritik/ritik_fenwick

Impelmented Fenwick Tree in C++

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	`1`	`+#include<bits/stdc++.h>`
	`2`	`+using namespace std;`
	`3`	`+`
	`4`	`+typedef long long ll;`
	`5`	`+const int S = 2;`
	`6`	`+const int MOD = 1000000000+7;`
	`7`	`+const int MODQ = 1000000000+7-1;`
	`8`	`+`
	`9`	`+struct mat_t {`
	`10`	`+ int m[S][S];`
	`11`	`+};`
	`12`	`+`
	`13`	`+// Function to calculate matrix multiplication`
	`14`	`+mat_t mat_mult(mat_t& a, mat_t& b) {`
	`15`	`+ mat_t c;`
	`16`	`+`
	`17`	`+ for(int i=0; i<S; i++)`
	`18`	`+ for(int j=0; j<S; j++)`
	`19`	`+ c.m[i][j] = 0;`
	`20`	`+`
	`21`	`+ for(int i=0; i<S; i++) {`
	`22`	`+ for(int k=0; k<S; k++) {`
	`23`	`+ for(int j=0; j<S; j++) {`
	`24`	`+ c.m[i][j] = (c.m[i][j]+ ll(a.m[i][k])*b.m[k][j] % MODQ) % MODQ;`
	`25`	`+ }`
	`26`	`+ }`
	`27`	`+ }`
	`28`	`+`
	`29`	`+ return c;`
	`30`	`+}`
	`31`	`+`
	`32`	`+`
	`33`	`+// Calculation Matrix Power in O(log(n)) ie A^n(where A is matrix)`
	`34`	`+// same as exponentiation power`
	`35`	`+mat_t mat_pow(mat_t a, int n) {`
	`36`	`+ mat_t w;`
	`37`	`+`
	`38`	`+ for(int i=0; i<S; i++) {`
	`39`	`+ for(int j=0; j<S; j++)`
	`40`	`+ w.m[i][j] = i==j;`
	`41`	`+ }`
	`42`	`+`
	`43`	`+`
	`44`	`+ while(n) {`
	`45`	`+ if(n&1) w = mat_mult(w, a);`
	`46`	`+ a = mat_mult(a, a);`
	`47`	`+ n/=2;`
	`48`	`+ }`
	`49`	`+`
	`50`	`+ return w;`
	`51`	`+}`
	`52`	`+`
	`53`	`+`
	`54`	`+int main() {`
	`55`	`+ int n; cin >> n;`
	`56`	`+`
	`57`	`+`
	`58`	`+ mat_t m;`
	`59`	`+ m.m[0][0] = m.m[0][1] = m.m[1][0] = 1;`
	`60`	`+ m.m[1][1] = 0;`
	`61`	`+`
	`62`	`+ m = mat_pow(m, n);`
	`63`	`+ cout << m.m[0][1] << endl;`
	`64`	`+}`

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	`1`	`+// Fenwick Tree implemented as a solution of a problem "http://codeforces.com/contest/1066/problem/C"`
	`2`	`+`
	`3`	`+`
	`4`	`+#include <bits/stdc++.h>`
	`5`	`+`
	`6`	`+using namespace std;`
	`7`	`+`
	`8`	`+#define IOS ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)`
	`9`	`+#define endl '\n'`
	`10`	`+#define ll long long`
	`11`	`+`
	`12`	`+const int N = 2e5 + 5;`
	`13`	`+`
	`14`	`+class Fenwick{`
	`15`	`+public:`
	`16`	`+ vector<int> bit = vector<int> (N, 0);`
	`17`	`+`
	`18`	`+ void add(int idx, int val){`
	`19`	`+ for(; idx < N && idx >= 0; idx = idx \| (idx + 1))`
	`20`	`+ bit[idx] += val;`
	`21`	`+ }`
	`22`	`+`
	`23`	`+ int sum(int r){`
	`24`	`+ int res = 0;`
	`25`	`+ for(;r >= 0;r = (r & (r + 1)) -1)`
	`26`	`+ res += bit[r];`
	`27`	`+ return res;`
	`28`	`+ }`
	`29`	`+}front, back;`
	`30`	`+`
	`31`	`+int main(){`
	`32`	`+ IOS;`
	`33`	`+ int q;cin>>q;`
	`34`	`+ int cnt = 0; map<int, int> m;`
	`35`	`+ while(q--){`
	`36`	`+ char c;int id;`
	`37`	`+ cin>>c>>id;`
	`38`	`+ if(c == 'L'){`
	`39`	`+ m[id] = cnt++;`
	`40`	`+ front.add(0, 1); front.add(cnt - 1, -1);`
	`41`	`+ back.add(cnt - 1, cnt - 1); back.add(cnt, -1*(cnt - 1));`
	`42`	`+ }`
	`43`	`+ else if(c == 'R'){`
	`44`	`+ m[id] = cnt++;`
	`45`	`+ back.add(0, 1); back.add(cnt -1, -1);`
	`46`	`+ front.add(cnt - 1, cnt - 1); front.add(cnt, - 1*(cnt - 1));`
	`47`	`+ }`
	`48`	`+ else{`
	`49`	`+ int idx = m[id];`
	`50`	`+ int p1 = front.sum(idx);`
	`51`	`+ int p2 = back.sum(idx);`
	`52`	`+ cout<<min(p1, p2)<<endl;`
	`53`	`+ }`
	`54`	`+ }`
	`55`	`+ return 0;`
	`56`	`+}`

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