### isRectangleCover 
from collections import defaultdict
from typing import *
def f_gold(rectangles: List[List[int]]) -> bool:
    area = 0
    minX, minY = rectangles[0][0], rectangles[0][1]
    maxX, maxY = rectangles[0][2], rectangles[0][3]
    cnt = defaultdict(int)
    for r in rectangles:
        area += (r[2] - r[0]) * (r[3] - r[1])
        minX = min(minX, r[0])
        minY = min(minY, r[1])
        maxX = max(maxX, r[2])
        maxY = max(maxY, r[3])
        cnt[(r[0], r[1])] += 1
        cnt[(r[0], r[3])] += 1
        cnt[(r[2], r[3])] += 1
        cnt[(r[2], r[1])] += 1
    if (
        area != (maxX - minX) * (maxY - minY)
        or cnt[(minX, minY)] != 1
        or cnt[(minX, maxY)] != 1
        or cnt[(maxX, maxY)] != 1
        or cnt[(maxX, minY)] != 1
    ):
        return False
    del cnt[(minX, minY)], cnt[(minX, maxY)], cnt[(maxX, maxY)], cnt[(maxX, minY)]
    return all(c == 2 or c == 4 for c in cnt.values())