题目链接：497. 非重叠矩形中的随机点
记录每个矩形的面积，以面积为权重采样。
from bisect import bisect_left
from random import random, randint
from typing import List
class Solution:
def __init__(self, rects: List[List[int]]):
ans, areas = 0, []
for a, b, x, y in rects:
ans += (x - a + 1) * (y - b + 1)
areas.append(ans)
self.ans, self.areas, self.rects = ans, areas, rects
def pick(self) -> List[int]:
a, b, x, y = self.rects[bisect_left(self.areas, random() * self.ans)]
return [randint(a, x), randint(b, y)]