segment trees questions added

Segment trees/rangeSumQuery.cpp

@@ -0,0 +1,59 @@
+#include<bits/stdc++.h>
+#define lld long long int
+#define ld long int
+#define str string
+#define dbl double
+using namespace std;
+
+
+void buildSegmentTree(int tree[],int values[],int index,int start,int end){
+	if(start>end) return;
+	if(start==end){
+		tree[index]=values[start];
+	}
+	else{
+		int mid = (start+end)/2;
+
+		//left subTree
+		buildSegmentTree(tree,values,2*index,start,mid);
+		//right subTree
+		buildSegmentTree(tree,values,2*index+1,mid+1,end);
+
+		tree[index] = tree[2*index]+tree[2*index+1];
+	}
+}
+
+void updateNode(int tree[],int s,int e,int index,int ind,int val){
+	if(ind<s or ind>e) return;
+	else if(s==e){
+		tree[index] = val;
+		return;
+	}
+	//left subtree call
+	int mid = (s+e)/2;
+	updateNode(tree,s,mid,2*index,ind,val);
+	updateNode(tree,mid+1,e,2*index+1,ind,val);
+	tree[index] = tree[2*index]+tree[2*index+1];
+	return;
+}
+
+int rangeSumQuery(int tree[],int index,int start,int end,int qStart,int qEnd){
+	if(qStart>end or qEnd<start) return 0;
+	if(qStart<=start and qEnd>=end) return tree[index];
+
+	int mid = (start+end)/2;
+	int left = rangeSumQuery(tree,2*index,start,mid,qStart,qEnd);
+	int right = rangeSumQuery(tree,2*index+1,mid+1,end,qStart,qEnd);
+	return left+right;
+
+}
+
+int main(){
+	int values[] = {1,3,2,-2,4,5,8,12,10,40};
+	int size = sizeof(values)/sizeof(values[0]);
+	int *segmentTree = new int[4*size+1];
+	buildSegmentTree(segmentTree,values,1,0,size-1);
+	updateNode(segmentTree,0,size-1,1,4,5);
+	cout<<rangeSumQuery(segmentTree,1,0,size-1,0,4);
+	return 0;
+}

Segment trees/segmentTrees.cpp

@@ -0,0 +1,79 @@
+#include<bits/stdc++.h>
+#define lld long long int
+#define ld long int
+#define str string
+#define dbl double
+using namespace std;
+
+//to update in a given range
+void updateRange(int tree[],int s,int e,int index,int qs,int qe,int inc){
+	if(s>qe or e<qs){
+		return;
+	}
+	if(s==e){
+		tree[index]+=inc;
+		return;
+	}
+
+	int mid = (s+e)/2;
+	updateRange(tree,s,mid,2*index,qs,qe,inc);
+	updateRange(tree,mid+1,e,2*index+1,qs,qe,inc);
+	tree[index] = min(tree[2*index],tree[2*index+1]);
+	return;
+}
+
+//to update at particular index
+void updateNode(int tree[],int s,int e,int index,int ind,int val){
+	if(ind<s or ind>e) return;
+	else if(s==e){
+		tree[index] = val;
+		return;
+	}
+	int mid = (s+e)/2;
+	updateNode(tree,s,mid,2*index,ind,val);
+	updateNode(tree,mid+1,e,2*index+1,ind,val);
+	tree[index] = min(tree[2*index],tree[2*index+1]);
+	return;
+}
+//building segment tree
+void buildSegmentTree(int tree[],int values[],int index,int start,int end){
+	if(start>end) return;
+	if(start==end){
+		tree[index]=values[start];
+	}
+	else{
+		int mid = (start+end)/2;
+
+		//left subTree
+		buildSegmentTree(tree,values,2*index,start,mid);
+		//right subTree
+		buildSegmentTree(tree,values,2*index+1,mid+1,end);
+
+		tree[index] = min(tree[2*index],tree[2*index+1]);
+	}
+}
+
+//give minimum element in given range
+int minElementQuery(int tree[],int index,int start,int end,int qStart,int qEnd){
+	if(qStart>end or qEnd<start) return INT_MAX;
+	if(qStart<=start and qEnd>=end) return tree[index];
+
+	int mid = (start+end)/2;
+	int left = minElementQuery(tree,2*index,start,mid,qStart,qEnd);
+	int right = minElementQuery(tree,2*index+1,mid+1,end,qStart,qEnd);
+	return min(left,right);
+
+}
+
+int main(){
+	int values[] = {1,3,2,-2,4,5};
+	int size = 6;
+	int *segmentTree = new int[4*size+1];
+	buildSegmentTree(segmentTree,values,1,0,size-1);
+	cout<<"minimum value is : "<<segmentTree[1]<<endl;
+	cout<<minElementQuery(segmentTree,1,0,size-1,0,5)<<endl;
+	updateNode(segmentTree,0,5,1,5,-8);
+	updateRange(segmentTree,0,5,1,0,3,-10);
+	cout<<minElementQuery(segmentTree,1,0,size-1,0,5)<<endl;
+	return 0;
+}