Sparse table algorithm

Competitive Coding/Search/sparse-table/sparse-table.cpp

@@ -0,0 +1,60 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define md 1000000007
+#define ll long long int
+#define vi vector<int>
+#define vll vector<i64>
+#define pb push_back
+#define all(c) (c).begin(),(c).end()
+int main()
+{
+
+    int n;
+    cin>>n;//Input the number of elements in the array.
+    int a[n];
+    for(int i=0;i<n;i++)
+    {
+        cin>>a[i];//read all the elements
+    }
+    int cols = log(n)/log(2);//Cols represent the no of coloumns in the sparse table .
+    int rows = n;//rows represent the no of rows in the sparse table
+    int lookup[rows][cols+1];
+    for(int i=0;i<=cols;i++)//This is the procedure to build a sparse table
+    {
+
+        for(int j=0;j<rows;j++)
+        {
+            if(i==0)
+                lookup[j][i]=j;
+            else
+            {
+
+                if(j+pow(2,i)<=n)
+                {
+
+                    if(a[lookup[j+(int)pow(2,i-1)][i-1]]>a[lookup[j][i-1]])//This is the procedure to create a sparse table for range minimum query. This statement of code can be appropriately changed for another type of query.
+                    lookup[j][i]=lookup[j][i-1];
+                    else
+                        lookup[j][i] = lookup[j+(int)pow(2,i-1)][i-1];
+
+                }
+            }
+            //cout<<stable[j][i]<<endl;
+        }
+    }
+
+    int left,right;
+    cin>>left>>right;
+    int k = right-left+1;//This represent the total length of the query range.
+
+    int col = (int)(log(k)/log(2));//This represent the coloumn we first look for in the sparse table.
+
+    int min1 = a[lookup[left-1][col]];
+    int remaining = k- pow(2,col);
+    int min2 = a[lookup[left+remaining-1][col]];
+
+    cout<<"minimum in the given range is :"<<min(min1,min2)<<endl;
+
+
+}