Min Stack Design in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the min stack's top pointer.

DSA C

typedef struct {
    int *stack;
    int *minStack;
    int top;
    int minTop;
} MinStack;

void initMinStack(MinStack *s) {
    s->top = [1];
    s->minTop = -1;
}

Drag options to blanks, or click blank then click option'

A-1

B0

C1

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing top to 0 causes off-by-one errors.

Using NULL for an integer top index is invalid.

The top index should start at -1 to indicate the stack is empty.

2fill in blank

medium

Complete the code to push a value onto the main stack.

DSA C

void push(MinStack *s, int val) {
    s->stack[++[1]] = val;
}

Drag options to blanks, or click blank then click option'

AminTop

Btop

Cstack

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Using minTop instead of top pushes to the wrong stack.

Not incrementing top causes overwriting the same position.

Incrementing top before assignment places the value correctly on the stack.

3fill in blank

hard

Fix the error in the condition to update the min stack when pushing a new value.

DSA C

if (s->minTop == -1 || val [1] s->minStack[s->minTop]) {
    s->minStack[++s->minTop] = val;
}

Drag options to blanks, or click blank then click option'

A>=

B>

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' causes incorrect min tracking.

Using '==' misses smaller values.

We push to minStack if val is less than or equal to current min, so use '<='.

4fill in blank

hard

Fill both blanks to correctly pop from the main stack and update the min stack if needed.

DSA C

int pop(MinStack *s) {
    int val = s->stack[s->[1]--];
    if (val == s->minStack[s->[2]]) {
        s->minTop--;
    }
    return val;
}

Drag options to blanks, or click blank then click option'

Atop

BminTop

Cstack

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up top and minTop indices.

Not decrementing top or minTop correctly.

Pop from main stack using top, and compare with minStack at minTop.

5fill in blank

hard

Fill all three blanks to return the current minimum value from the min stack.

DSA C

int getMin(MinStack *s) {
    if (s->[1] == -1) {
        return [2]; // empty stack case
    }
    return s->minStack[s->[3]];
}

Drag options to blanks, or click blank then click option'

AminTop

B-1

Dtop

Attempts:

3 left

💡 Hint

Common Mistakes

Checking top instead of minTop for empty.

Returning wrong index from minStack.

Check if minTop is -1 (empty), return -1 as error, else return minStack[minTop].