public boolean deleteNode(Node curnt){
		if (curnt.leftChld==null && curnt.rightChld==null) {	//if no child
			if(curnt==root)
				root=null;
			else if(isLeftch)
				parent.leftChld=null;
			else 
				parent.rightChld=null;
		}else if(curnt.rightChld==null){		//no rightchild replace left sub tree
			if(curnt==root)
				root=curnt.leftChld;
			else if(isLeftch)
				parent.leftChld=curnt.leftChld;
			else
				parent.rightChld=curnt.leftChld;
		}else if(curnt.leftChld==null){			//no left child replace right subtree
			if(curnt==root)
				root=curnt.rightChld;
			else if(isLeftch)
				parent.leftChld=curnt.rightChld;
			else
				parent.rightChld=curnt.rightChld;
		}else{									// have left ,right child
			Node sucssesor=getSuccessor(curnt);		//find the best node to replace
			if(curnt==root)
				root=sucssesor;
			else if(isLeftch)
				parent.leftChld=sucssesor;
			else
				parent.rightChld=sucssesor;
			sucssesor.leftChld=curnt.leftChld;
		}
		
		return true;
	}