Important Questions

Fill Water questions

84. Largest Rectangle in Histogram (https://leetcode.com/problems/largest-rectangle-in-histogram/description/)

• Needs to build a increasing stack and it will allow you let where is left boundary.

85. Maximal Rectangle (https://leetcode.com/problems/maximal-square/description/) (Question 84's further question)

Square && Rectangle

836. Rectangle Overlap (https://leetcode.com/problems/rectangle-overlap/description/)

• Good question and you just make sure rec2's x1 >= rec1's x2 ... 4 conditions

223. Rectangle Area (https://leetcode.com/problems/rectangle-area/description/)

• 836 题升级版

Matrix

54. Spiral Matrix (https://leetcode.com/problems/spiral-matrix/description/)

• You need to traverse more nodes in horizontal.
• Mark top-left and bottom-right point.

Frequent Questions

What's difference between Comparator and Comparable?

1. PriorityQueue<Cell> heap = new PriorityQueue<Cell>(16);
- class Cell implements Comparable<Cell>!

2. PriorityQueue<Cell> heap = new PriorityQueue<Cell>(16n new MyComparator());
- class MyComparator implements Comparator<Cell>!

// Class whose objects to be sorted must implement this Comparable interface
public interface Comparable {
   public int compareTo(Object obj);
}

// Some third class can implement this interface to sort.
public interface Comparator {
    public boolean equals(Object obj);

    public int compare(T o1, T o2);
}