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GATE CS 2018 - Data Structures Quiz 3
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Question 1
The best data structure to check whether an arithmetic expression has balanced parentheses is a
Question 2
The following postfix expression with single digit operands is evaluated using a stack:
8 2 3 ∧/ 2 3 * + 5 1 * –
Note that ∧ is the exponentiation operator. The top two elements of the stack after the first * is evaluated are:
8 2 3 ∧/ 2 3 * + 5 1 * –
Note that ∧ is the exponentiation operator. The top two elements of the stack after the first * is evaluated are:
Question 3
An implementation of a queue Q, using two stacks S1 and S2, is given below:
void insert (Q, x) {
push (S1, x);
}
void delete (Q) {
if (stack-empty(S2)) then
if (stack-empty(S1)) then {
print(“Q is empty”);
return;
}
else while (!(stack-empty(S1))){
x=pop(S1);
push(S2,x);
}
x=pop(S2);
}
Let n insert and m(≤n) delete operations be performed in an arbitrary order on an empty queue Q. Let x and y be the number of push and pop operations performed respectively in the process. Which one of the following is true for all m and n?
Question 4
To evaluate an expression without any embedded function calls
Question 5
Let S be a stack of size n ≥1. Starting with the empty stack, suppose we push the first n natural numbers in sequence, and then perform n pop operations. Assume that Push and Pop operations take X seconds each, and Y seconds elapse between the end of one such stack operation and the start of the next operation. For m ≥1, define the stack-life of m as the time elapsed from the end of Push(m) to the start of the pop operation that removes m from S. The average stack-life of an element of this stack is
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Jul 9GATE & PSU CS
