 end prefix
The evaluation of the tree takes place by reading the postfix expression one symbol at a time.If the symbol is an operand, a one-node tree is created and its pointer is pushed onto a stack.If the symbol is an operator, the pointers to two trees "T1" and "T2" are popped from the stack and a new tree whose root is the operator and whose left and right children point to "T2" and "T1" respectively is formed .