lazy propogating segment Tree.

Read About Lazy Trees:
http://www.geeksforgeeks.org/lazy-propagation-in-segment-tree/

Build 0:
--> update and retrieval of range sum.
--> all nodes are initialized with zero.
--> initialization with given values
--> only integer values are accepted

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Range Query -- O(log N)
Range Update O(log N)

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Constructors:

1. LazyTree()
2. LazyTree(long long)
3. LazyTree(long long, long long)
4. LazyTree(vector)

Functions available:

1. long long size()
2. void update(long long, long long)
3. void update(long long, long long, long long)
4. long long retrieve(long long, long long)

***usage & discription: ***

1. LazyTree() : creates an empty Tree. with no nodes at all. useless.
   

LazyTree L();

2. LazyTree(long long size) : creates tree with Size = size, with default value = 0, for every node.
   

LazyTree L(4);

3. LazyTree(long long size, long long m) : creates tree with Size = size, with default value = m, for every node.
   

LazyTree L(4,2);

4. LazyTree(vector ) : creates a tree from the array.
   

vector<long long> vect(4,2); //array values can be different
LazyTree L(vect);

1. long long size() : returns initialized size. useless.
2. void update(long long pos, long long val) : element at position = pos, increments with value = val;

L.update(4,7); 
// equivalent to L.update(4,4,7);

3. void update(long long L, long long R, long long val) : range update function. increments the values = val, in the range [L,R].

L.update(4,5,7);

4. long long retrieve(long long L, long long R) : query the sum in range [L,R]

L.retrieve(4,5);	

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