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essential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） All trademarks are either the home of Central Backyard garden & Pet Enterprise, its subsidiaries, divisions, affiliated and/or related businesses or even the house of their respective proprietors. ● सीधे ऐप में ... https://pearlaquatics.my/how-to-keep-a-freshwater-aquarium-clean/