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 possibly the home of Central Backyard & Pet Organization, its subsidiaries, divisions, affiliated and/or connected businesses or maybe the assets of their respective owners. 一周 Commemorates ... https://pearlaquatics.my/4-tips-to-follow-when-building-a-fish-pond/