Write a stack-based algorithm that will check a sequence of tokens to see if it is a valid postfix expression. For example, 1 3 * + and + 4 10 are not well formed. (Hint: adapt the postfix evaluation algorithm.)

- In class HashTable implement a hash table and consider the following:(i) Keys are integers (therefore also negative!) and should be stored in the tableint[] data.(ii) As a hash function take h(x) = (x · 701) mod 2000. The size of the table istherefore 2000. Be careful when computing the index of a negative key. Forexample, the index of the key x = −10 ish(−10) = (−7010) mod 2000 = (2000(−4) + 990) mod 2000 = 990.Hence, indices should be non-negative integers between 0 and 1999!(iii) Implement insert, which takes an integer and inserts it into a table. Themethod returns true, if the insertion is successful. If an element is already inthe table, the function insert should return false.(iv) Implement search, which takes an integer and finds it in the table. The methodreturns true, if the search is successful and false otherwise.(v) Implement delete, which takes an integer and deletes it form the table. Themethod returns true, if the deletion is successful and false otherwise.(vi)…

For JAVA.

public boolean isprefix(String s1, String s2) {int i = 0;if(s1.length > s2.length) return false;while(i < s1.length) {if(s1[i] != s2[i])return false;i++;}return true;}   Use the active operation approach and determine the exact number of times the active operation is executed in the worst case.  Express your answer in terms of n, the length of the string s1. Hint:  simplify your final answer as much as possible, and do not put spaces in your answer.  Use juxtaposition for the multiplication operator, for example to write "nine times n" write "9n" not "9xn" or "9*n";  to write "four times (n+2)" write "4(n+2)", not "4x(n+2)" or "4*(n+2)".  Do not write your answer in Big-O notation.  Write the exact number of lines executed.