status of problem added to each file

Author: yash9724

practice/a.exe

@@ -0,0 +1,116 @@
+// Problem:
+// We have an array a[0...n-1]. We should be able to efficiently 
+// find the minimum value from index qs(query start) to qe(query end)
+// where 0 <= qs <= qe <= n-1.
+// Also write code for efficient updates on an element
+// or a range of element
+
+#include<iostream>
+#include<climits>
+using namespace std;
+
+void buildTree(int* a, int s, int e, int* tree, int index){
+ // base case
+ if(s == e){
+ tree[index] = a[s];
+ return;
+ }
+
+ // recursive case
+ int mid = (s+e)/2;
+ buildTree(a, s, mid, tree, 2*index);
+ buildTree(a, mid+1, e, tree, 2*index+1);
+ tree[index] = min(tree[2*index], tree[2*index+1]);
+ return;
+}
+
+int query(int* tree, int ss, int se, int qs, int qe, int index){
+ // complete overlap
+ if(ss>=qs && se<=qe)
+ return tree[index];
+
+ // no overlap
+ if(ss>qe || se<qs)
+ return INT_MAX;
+ 
+ // partial overlap
+ int mid = (ss+se)/2;
+ int leftMin = query(tree, ss, mid, qs, qe, 2*index);
+ int rightMin = query(tree, mid+1, se, qs, qe, 2*index+1);
+ return min(leftMin, rightMin);
+}
+
+// updating single index
+void updateIndex(int* tree, int ss, int se, int i, int incr, int index){
+ // out of bounds range
+ if(i>se || i<ss){
+ return;
+ }
+
+ // leaf node
+ if(ss == se){
+ tree[index] = tree[index] + incr;
+ return;
+ }
+
+ // partial overlap - call left and right child
+ int mid = (ss+se)/2;
+ updateIndex(tree, ss, mid, i, incr, 2*index);
+ updateIndex(tree, mid+1, se, i, incr, 2*index+1);
+ tree[index] = min(tree[2*index], tree[2*index+1]);
+ return;
+}
+
+// updating range of indices
+int updateRange(int* tree, int ss, int se, int l, int r, int incr, int index){
+ // out of bounds
+ if(l > se || r < ss)
+ return;
+
+ // leaf node
+ if(ss == se){
+ tree[index] += incr;
+ return;
+ }
+
+ // partial overlap - call left and right child
+ int mid = (ss+se)/2;
+ updateRange(tree, ss, mid, l, r, incr, 2*index);
+ updateRange(tree, mid+1, se, l, r, 2*indx+1);
+ tree[index] = min(tree[2*index], tree[2*index+1]);
+ return;
+}
+
+
+int main(){
+ int n;
+ // cin>>n;
+ int a[] = {1, 3, 2, -5, 6, 4};
+ n = sizeof(a)/sizeof(int);
+ // for(int i = 0 ; i < n ; i++)
+ // cin>>a[i];
+ 
+ int* tree = new int[4*n+1];
+ buildTree(a, 0, n-1, tree, 1);
+
+ // print tree
+ for(int i = 1; i<=4*n; i++){
+ cout<<tree[i]<<" ";
+ }
+ cout<<endl;
+
+ // query
+ int l=2, r=5;
+ // cin>>l>>r;
+ cout<<query(tree, 0, n-1, l, r, 1);
+
+ // update index
+ updateIndex(tree, 0, n-1, 4, -3, 1);
+
+ // print tree
+ for(int i = 1; i<=4*n; i++){
+ cout<<tree[i]<<" ";
+ }
+ cout<<endl;
+ return 0;
+}