squareRootDecomp

Data Structures/Trees/squareRootDecomposition.cpp

@@ -0,0 +1,112 @@
+// Created on 20-07-2019 20:13:23 by necronomicon
+#include <iostream>
+#include <string>
+#include <vector>
+#include <algorithm>
+#include <sstream>
+#include <queue>
+#include <deque>
+#include <bitset>
+#include <iterator>
+#include <list>
+#include <stack>
+#include <map>
+#include <set>
+#include <unordered_map>
+#include <unordered_set>
+#include <functional>
+#include <numeric>
+#include <utility>
+#include <limits>
+#include <iomanip>
+#include <ctime>
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+#include <cstdlib>
+#include <cassert>
+using namespace std;
+
+#define MP make_pair
+#define PB push_back
+#define ARR_MAX (int)1e5 //Max array length
+#define INF (int)1e9 //10^9
+#define EPS 1e-9 //10^-9
+#define MOD 1000000007 //10^9+7
+#define PI 3.1415926535897932384626433832795
+typedef long int int32;
+typedef unsigned long int uint32;
+typedef long long int int64;
+typedef unsigned long long int  uint64;
+typedef pair<int, int> Pii;
+typedef vector<int> Vi;
+typedef vector<string> Vs;
+typedef vector<Pii> VPii;
+typedef vector<Vi> VVi;
+typedef map<int,int> Mii;
+typedef set<int> Si;
+typedef multimap<int,int> MMii;
+typedef multiset<int> MSi;
+typedef unordered_map<int,int> UMii;
+typedef unordered_set<int> USi;
+typedef unordered_multimap<int,int> UMMii;
+typedef unordered_multiset<int> UMSi;
+typedef priority_queue<int> PQi;
+typedef queue<int> Qi;
+typedef deque<int> DQi;
+
+/* 
+RSQ tree
+doesnt use mo algo
+*/
+
+
+// global variables
+int N, blocks;
+Vi V, SQ;
+
+void preProcess(){
+    N = V.size();
+    blocks = (int) sqrt(N + 0.0) + 1; // number of blocks
+    SQ = Vi(blocks, 0);
+    for (int i = 0; i < N; i++)
+    {
+        SQ[i/blocks] += V[i];
+    }
+}
+
+void update(int idx, int val){
+    int block = idx/blocks;
+    int diff = val - V[idx];
+    V[idx] += diff;
+    SQ[block] += diff;
+}
+
+int query(int l, int r){
+    int blockL = l/blocks, blockR = r/blocks;
+    int sum = 0;
+    if(blockL == blockR){
+        for (int i = l; i <= r; i++) sum += V[i]; // when both lie inside a block just add them in O(r-l)
+    }
+    else{
+        for (int i = l; i <= (blockL+1)*(blocks-1); i++) sum += V[i]; // left block
+        for (int i =  (blockR)*(blocks); i <= r; i++) sum += V[i]; // right block
+        for (int i = blockL+1; i < blockR; i++) sum += SQ[i]; // add complete block in between
+    }
+    return sum;
+}
+
+int main (int argc, char const *argv[]) {
+	V = {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1};
+    preProcess();
+    int n;
+    cin >> n;
+    for (int i = 0; i < n; i++)
+    {
+        int l, r;
+        cin >> l >> r;
+        cout << query(l, r) << endl;
+    }
+
+    return EXIT_SUCCESS;
+}