再用n2的时间（两重循环）枚举d-c，并将b-c的值作为键，在Hash数组中查找是否存在。如果能找到critical相同的node点，则找到了一组满足 D-c = a+b的值。（注意检查a b c d 四个数不重复） Are living plants are more than just attractive features in a very freshwater aquarium. They contribute to oxygenation, support sustain drinking water quality, and provide natural habitats for fish. 三個月 返 回 ... https://pearlaquatics.my/7-tips-to-control-and-prevent-algae/