Algorith Interview:
1) calculate sum of nested array
2) two string might be the same or not, but elements rearranged, make code to find are they the same or not
3) class Stack {}
const stack = new Stack{}
stack.customPush(1);
stack.customPush(2);
stack.customPush(3);
stack.customPop(); returns => 3
stack.customPop(); returns => 2