algorithm_codes/PersistentSegmentTree.cpp at master · Algoskills/algorithm_codes · GitHub

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#include<iostream>

usingnamespacestd;

int a[]={5,9,1,2,3};

// Structure of nodes of tree
structnode
{
int val;
	node *left,*right;

node()
	{

	}

node(node *l,node *r,int v)
	{
 left=l;
 right=r;
 val=v;
	}
};

//array to store versions
node *version[3];


//function to build version 0
voidbuild(node *n,int low, int high)
{
	cout<<"Array: ";
for (int i = low; i <= high; ++i)
	{
 cout<<a[i]<<"";
	}
	cout<<endl;
if(low==high)
	{
 n->val=a[low];
return;
	}

int mid=(low+high)/2;
	n->left= newnode(NULL,NULL,0);
	n->right= newnode(NULL,NULL,0);

build(n->left,low,mid);
build(n->right,mid+1,high);
	n->val= n->left->val + n->right->val;
}


//function to make other version(to update previous version)
voidupdate(node *prev, node *cur, int low, int high, int idx, int value)
{
if(idx>high || idx<low || low>high)
return;

if(low==high)
	{
 cur->val=value;
return;
	}
int mid=(low+high)/2;

if(idx<=mid)
	{
 cur->right=prev->right;

 cur->left= newnode(NULL,NULL,0);
update(prev->left,cur->left,low,mid,idx,value);
	}
else
	{
 cur->left=prev->left;
 cur->right= newnode(NULL,NULL,0);
update(prev->right,cur->right,mid+1,high,idx,value);
	}
	cur->val = cur->left->val + cur->right->val;
}

//For query
intquery(node *n, int low, int high, int l, int r)
{
if(l>high || r<low || low>high)
	{
return0;
	}

if(l<=low && r>=high)
	{
return n->val;
	}
int mid=(low+high)/2;
int x= query(n->left, low, mid, l, r);
int y= query(n->right, mid+1, high, l, r);

return x+y;
}
//driver function
intmain()
{

int n= sizeof(a)/sizeof(a[0]);

	node *root= newnode(NULL,NULL,0);

build(root,0,n-1);

	version[0]=root;

	version[1]=newnode(NULL,NULL,0);

update(version[0],version[1],0,n-1,3,1);

	version[2]=newnode(NULL,NULL,0);

update(version[1],version[2],0,n-1,4,8);


	cout << "In version 0 , the sum in range(0,2) is " << query(version[0], 0, n-1, 0, 2) << endl;

	cout << "In version 1 ,the sum in range(1,3) is "<< query(version[1], 0, n-1, 1, 3) << endl;

 cout << "In version 2 , the sum in range(1,4) is "<< query(version[2], 0, n-1, 1, 4) << endl;

return0;

}