Nine notes

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given an array of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].

Find the contiguous subarray within an array (containing at least one number) which has the largest product.

Find the contiguous subarray within an array (containing at least one number) which has the largest sum.

There are N gas stations along a circular route, where the amount of gas at station i is gas[i].

Find the total area covered by two rectilinear rectangles in a 2D plane.

Solutions with two stacks

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class MinStack {
    Stack<Integer> nums = new Stack<Integer>();
    Stack<Integer> min = new Stack<Integer>();
    
    public void push(int x) {
        nums.push(x);
        if (!min.empty() && min.peek() < x){
            min.push(min.peek());
        }else{
            min.push(x);
        }
    }

    public void pop() {
        if (!nums.empty() && !min.empty()){
            nums.pop();
            min.pop();
        }
    }

    public int top() {
        return nums.peek();
    }

    public int getMin() {
        return min.peek();
    }
}

Implement the following operations of a queue using stacks.

Implement the following operations of a stack using queues.

A peak element is an element that is greater than its neighbors.

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

Given an input string, reverse the string word by word.

Implement an iterator to flatten a 2d vector.

Paint House I

There are a row of n houses, each house can be painted with one of the three colors: red, blue or green. The cost of painting each house with a certain color is different. You have to paint all the houses such that no two adjacent houses have the same color.