1. Tell me about yourself.
2. Implement Queue using stacks.
3. Find first non-repeated character in a given string.

Question

1. Tell me about yourself.
2. Implement Queue using stacks.
3. Find first non-repeated character in a given string.

Anonymous · Accepted Answer

class MyStack {
    // Push element x onto stack.
    List q1 = new LinkedList();
    List q2 = new LinkedList();
    public void push(int x) {
        if(q1.isEmpty()){
            q1.add(x);
            while (!q2.isEmpty()){
                q1.add(q2.remove(0));
            }
        }else{
            q2.add(x);
            while(!q1.isEmpty()){
                q2.add(q1.remove(0));
            }
        }
    }

    // Removes the element on top of the stack.
    public void pop() {
        if(q1.isEmpty()){
            q2.remove(0);
        }else{
            q1.remove(0);
        }
    }

    // Get the top element.
    public int top() {
        if(q1.isEmpty()){
            return q2.get(0);
        } else{
            return q1.get(0);
        }
    }

    // Return whether the stack is empty.
    public boolean empty() {
        return q1.isEmpty() && q2.isEmpty();
    }
}

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