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） Reside plants are more than just decorative components inside a freshwater aquarium. They contribute to oxygenation, assist sustain drinking water quality, and provide natural habitats for fish. 一天 - 更高级的... https://pearlaquatics.my/author/jasun/