RectangleOverlap863.java

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

public class RectangleOverlap863 {
    public boolean isRectangleOverlap(int[] rec1, int[] rec2) {
        return isIntervalOverlap(rec1[0], rec1[2], rec2[0], rec2[2]) && isIntervalOverlap(rec1[1], rec1[3], rec2[1], rec2[3]);
    }

    private boolean isIntervalOverlap(int a1, int a2, int b1, int b2) {
        return !(a2 <= b1 || b2 <= a1);
    }


    public boolean isRectangleOverlap2(int[] rec1, int[] rec2) {
        return !(rec1[2] <= rec2[0] ||   // left
                rec1[3] <= rec2[1] ||   // bottom
                rec1[0] >= rec2[2] ||   // right
                rec1[1] >= rec2[3]);    // top
    }

}