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     * File:   main.cpp
     * Author: akash
     * Created on 12 August, 2015, 4:57 PM
    #include <stdio.h>
     #include <stdlib.h>
    struct node
     int data;
     struct node* next;
     //void push(struct **node top_head,int dataToEnter);
     //int getCount(struct *node top_head);
    void push(struct node** top_head,int dataToEnter)
     struct node* add_node = (struct node*) malloc(sizeof(struct node));
    add_node->data = dataToEnter;
     add_node->next = (*top_head);
     (*top_head) = add_node;
    int getCount(struct node* top_head){
     if (top_head == NULL)
     return 0;
    // count is 1 + count of remaining list
     return 1 + getCount(top_head->next);
    int main(){
     struct node* head = NULL;
    push(&head, 10);
     push(&head, 20);
     push(&head, 30);
     push(&head, 40);
     push(&head, 20);
     push(&head, 30);
    printf("Nodes Count is %d", getCount(head));
     return 0;

    This answer accepted by SherlockHolmes. on 6th November 2015 Earned 20 points.

    • 1 answers
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  • The letter “E”.

    considering word “week”, it has two similar letters that is “E”
    and for the word year, has one “E”.

    This answer accepted by SherlockHolmes. on 14th September 2016 Earned 20 points.

    • 1 answers
    • 0 votes
  • 1   2    3


    SUM            = 1+2+3=6
    PRODUCT = 1*2*3 =6

    • 2 answers
    • 1 votes
  • Four Coins

    Three coins placed flat on the table in a triangle(touching each other) and put the fourth one on top of them in the middle.

    • 1 answers
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    • 3 answers
    • 2 votes
  • Take any 13 cards and flip them all. Rest 39 cards will make another pile. These two piles will have the same number of cards facing up. Why? Well, say out of those 13 selected 0 \leq n \leq 13 cards are facing up.  Which means that in the pile with 39 cards there will be 13-n cards facing up. When you flip all 13 cards, number of cards facing up now becomes 13-n which is equal to what the other pile have.

    • 1 answers
    • 1 votes

    Yes, the ant will reach the car. Calculus tells us exactly when:

    if a < 0, then exp(c/a) < 1 and t < 0, which means no solution. The faster the car is, the greater [exp(c/a)]/c is and thus, the longer it is for the ant to reach the car.

    • 2 answers
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  • This is Ant on a rubber rope problem

    The worm will eventually reach the end.
    The key to understand this is that the proportion between the total length of the  rubber Band and the length walked by the worn can only increase with time, as it will eventually approach one.

    The problem seems impossible because we are looking worm and the rubber Band moving independently.

    Things become a little more imaginable – “When we realize that the Worm is on the rubber Band, and the portion of the rubber Band behind the worm also stretches just as the portion in front of the worm does,”

    The mathematics are complex, but think of the entire picture of the worm and the rubber Band.

    At 0 Hour, the worm is at the very end of the rubber Band, and has 100 percent of the rubber Band in front of it.
    At 1 Hour, it’s true that the Worms’s task is considerably increased, but it doesn’t have one hundred percent of the rubber Band in front of it.
    And that tiny percentage of the rubber Band that the anworm has traversed will stretch in proportion, just like the rest of the rubber Band.

    So, Percentage of distance to be covered is increasing in same proportion to the Distance already covered.

    Percent of Distance traveled is increasing     DIRECTLY PROPORTIONAL to        Increase in distance to be traveled.

    • 2 answers
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  • It is pretty interesting. Not only can it tell us whether the number is divisible by 7 but also the exact remainder obtained if the number is divided by 7.

    How this works is that each node is connected to a remainder by 7. That is each node has a unique number in [0..6] associated with it. And the rest is simple modular arithmetic.

    To enumerate the associated numbers, the bottom-most node has 0 associated with it. From there, keep following the black arrows- you’ll obtain the node associated with the next number. As in the right-most node is associated with 1, the topmost with 2 and so on. You’ll notice that the leftmost node is associated with 6 which in turn leads to 0.

    You should also notice that the white arrows lead up from nodes n mod 7 to nodes n10 mod 7. This is important.

    Now let us consider a number N with digits N1,N2...Nm with Nm being the unit digit.

    We begin applying the given algorithm:

    1. We follow the black arrow N1 number of times and arrive at the node N1 mod 7.
    2. Next we follow the white arrow to arrive at the node N110 mod 7.
    3. We repeat step 1 to follow the black arrow N2 number of times. Now we are at N110+N2 mod 7.
    4. We follow step 2 again to arrive at N1100+N210 mod 7.
    5. Applying the same procedure until the last digit, we finally arrive at the node N110m1+N210m2+..+Nm mod 7 which equals N mod 7. If we are at the bottommost node, then we conclude that N mod 7=0 and hence proving the divisibility of N by 7.

    If anything is unclear, feel free to leave comments.

    • 2 answers
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  • If you’re interested in the concept, type in the phrase “casting out nines” in your search engine of choice.
    In the example you gave, the basic idea is that you know that X and Y have the same remainder when divided by 9 since they share the same digits1. Hence, the difference must be a multiple of 9. Since we know the sum of the digits of any multiple of 9 is itself a multiple of 9, you can deduce the last digit.
    (In the case that the sum is itself a multiple of 9, you can use the fact that they hid a non-zero digit to deduce that the remaining digit is in fact a 9.)

    • 2 answers
    • 1 votes