SDE - Intern

1. The idea is to use stack. 
2. Iterate through the given expression and for each character in the expression, if the character is a open parenthesis ‘(‘ or any of the operators or operands, push it to the top of the stack. 
3. If the character is close parenthesis ‘)’, then pop characters from the stack till matching open parenthesis ‘(‘ is found and a counter is used, whose value is incremented for every character encountered till the opening parenthesis ‘(‘ is found. 
4. If the number of characters encountered between the opening and closing parenthesis pair, which is equal to the value of the counter, is less than 1, then a pair of duplicate parenthesis is found else there is no occurrence of redundant parenthesis pairs. 
5. For example, (((a+b))+c) has duplicate brackets around “a+b”. When the second “)” after a+b is encountered, the stack contains “((“. Since the top of stack is opening bracket, it can be concluded that there are duplicate brackets.

1. Sort list 1 by always comparing with head/first of list 2 and swapping if required
2. After each head/first swap, perform insertion of the swapped element into correct position in list 2 which will eventually sort list 2 at the end. 
For every swapped item from list 1, perform insertion sort in list 2 to find its correct position so that when list 1 is sorted, list 2 is also sorted.

Tip 1 : Use Trie Data structure
Tip 2 : Explain clearly how it works.

Tip 1 : Do practice for SQL queries.