836. Rectangle Overlap

A rectangle is represented as a list [x1, y1, x2, y2], where (x1, y1) are the coordinates of its bottom-left corner, and (x2, y2) are the coordinates of its top-right corner.

Two rectangles overlap if the area of their intersection is positive.  To be clear, two rectangles that only touch at the corner or edges do not overlap.

Given two (axis-aligned) rectangles, return whether they overlap.

Example 1:

Input: rec1 = [0,0,2,2], rec2 = [1,1,3,3]
Output: true

Example 2:

Input: rec1 = [0,0,1,1], rec2 = [1,0,2,1]
Output: false

Notes:

1. Both rectangles rec1 and rec2 are lists of 4 integers.
2. All coordinates in rectangles will be between -10^9 and 10^9.

//Time: O(1), Space: O(1) 
//思路就是分别比较两个矩形的长和宽，对于一条线段相交条件就是两个远离的端点和中间两点满足条件即可
  public boolean isRectangleOverlap(int[] rec1, int[] rec2) {
        if (rec1 == null || rec1.length == 0 || rec2 == null || rec2.length == 0) {
            return false;
        }
        
        return rec1[0] < rec2[2] && rec2[0] < rec1[2] && rec1[3] > rec2[1] && rec2[3] > rec1[1];
    }