Here is the rank list for the series "C For Code" after 2 contests. 6 contests are still left, lets see how much it changes:

Rank	Name	Prob 1	Prob 2	Prob 3	Contest 2	Grand Total
1	Vijay Tripathi	189.94	269.42	460.42	919.78	1773.93
2	Karan Khullar	195.89	203.44	500.00	899.33	1743.24
3	Amit Jain	197.57	150.00	388.29	735.86	1483.92
4	Gourav Pathak	195.94	0.00	371.30	567.24	1387.71
5	Anuj Kumar	177.63	150.00	399.12	726.75	1270.99
6	Vaibhav Sethi	200.00	150.00	0.00	350.00	1207.66
7	Mayank Yadav	164.00	207.36	0.00	371.36	814.74
8	Abhinav Saraswat	176.70	0.00	0.00	176.70	739.41
9	Vishesh Srivastava	193.72	150.00	0.00	343.72	736.79
10	Prakhar Rastogi	195.78	150.00	0.00	345.78	699.89
11	Sumit Awasthi	140.02	0.00	0.00	140.02	661.36
12	Ashish Ranjan	194.69	0.00	0.00	194.69	623.20
13	Inderjeet Yadav	182.91	0.00	0.00	182.91	599.87
14	Prakhar Rastogi	197.63	0.00	0.00	197.63	560.28
15	Prateek Nischal	155.63	204.14	0.00	359.77	556.58
16	Arup Das	190.83	219.94	0.00	410.78	547.59
17	Anant Kumar	196.48	161.25	0.00	357.73	526.97
18	Nitish Gupta	174.59	150.00	0.00	324.59	519.61
19	Law Kumar	100.00	0.00	0.00	100.00	475.00
20	Shashank Shekhar	197.31	270.00	0.00	467.31	467.31
21	John Bupit (Mohit)	183.83	273.03	0.00	456.86	456.86
22	Aman Jain	188.59	0.00	0.00	188.59	416.59
23	Rohit Kumar	189.69	0.00	0.00	189.69	387.13
24	Robin Parashar	191.89	0.00	0.00	191.89	386.19
25	Yogendra Singh Vimal	187.41	0.00	0.00	187.41	382.02
26	Sujay Raj	184.56	0.00	0.00	184.56	374.56
27	Anil Bakhla	182.06	0.00	0.00	182.06	370.78
28	Edge_123 (Jayant)	165.81	0.00	0.00	165.81	363.65
29	Ashawani Chandil	188.89	0.00	0.00	188.89	361.43
30	Siddharth Behera	0.00	0.00	0.00	0.00	361.04
31	Adhiraj Nakhe	191.24	163.97	0.00	355.21	355.21
32	Pawan Deshmukh	188.87	0.00	0.00	188.87	352.76
33	Saurabh Prasad	176.26	0.00	0.00	176.26	351.43
34	Ashish Bahukhandi	189.61	0.00	0.00	189.61	337.59
35	Nikhil Dubey	193.28	0.00	0.00	193.28	335.11
36	Ravi Gupta	187.02	0.00	0.00	187.02	332.94
37	Anuj Asher	129.78	0.00	0.00	129.78	326.94
38	Pavan Kriplani	192.19	0.00	0.00	192.19	317.78
39	Ankur Agrawal	188.69	0.00	0.00	188.69	312.09
40	Rahul Kumar Yadav	194.57	0.00	0.00	194.57	294.57
41	Gayathri Devi	133.37	0.00	0.00	133.37	291.22
42	Deep Kumar Sakre	151.85	0.00	0.00	151.85	288.89
43	Akshay Agrawal	188.44	0.00	0.00	188.44	288.44
44	Anil Yadav	186.35	0.00	0.00	186.35	286.35
45	Anjaney Pandey	100.00	0.00	0.00	100.00	283.00
46	Sravan Kumar	134.19	0.00	0.00	134.19	234.19
47	Swapnil Gupta	117.87	0.00	0.00	117.87	217.87
48	Deepak Gupta	110.15	0.00	0.00	110.15	210.15
49	Anish Somani	106.44	0.00	0.00	106.44	206.44
50	Hitesh Sharma	100.00	0.00	0.00	100.00	200.00
51	Rohit Kumar	0.00	0.00	0.00	0.00	195.46
52	Harshit Gupta	188.65	0.00	0.00	188.65	188.65
53	Sakshi Gopal	0.00	0.00	0.00	0.00	188.15
54	Ashish Awasthi	0.00	0.00	0.00	0.00	186.43
55	Tushar Turkar	174.19	0.00	0.00	174.19	174.19
56	Kumar Vikram	171.35	0.00	0.00	171.35	171.35
57	Umang Popli	170.07	0.00	0.00	170.07	170.07
58	Naveen Yadav	167.07	0.00	0.00	167.07	167.07
59	Saurav Kothari	0.00	0.00	0.00	0.00	166.50
60	Abhishek Raj	164.50	0.00	0.00	164.50	164.50
61	Niraj Kumar	0.00	0.00	0.00	0.00	148.98
62	Priya Kumari	144.87	0.00	0.00	144.87	144.87
63	Mohit Srivastava	0.00	0.00	0.00	0.00	139.02
64	Prakash Tripathi	0.00	0.00	0.00	0.00	133.02
65	Raghav Agarwal	117.26	0.00	0.00	117.26	117.26
66	Pawan Kumar	107.06	0.00	0.00	107.06	107.06
67	Tarun Jindal	103.11	0.00	0.00	103.11	103.11
68	Aadil Khan	100.00	0.00	0.00	100.00	100.00
68	Rajan Ranbir	100.00	0.00	0.00	100.00	100.00
68	Amit Kumar Verma	100.00	0.00	0.00	100.00	100.00
68	Sshantanu Agarwal	100.00	0.00	0.00	100.00	100.00
68	Gaurav Patel	100.00	0.00	0.00	100.00	100.00
68	Mohammad Ahmed	100.00	0.00	0.00	100.00	100.00
68	Shubham Dixit	100.00	0.00	0.00	100.00	100.00
68	Kuljeet Singh	100.00	0.00	0.00	100.00	100.00
68	Yogendra Singh	100.00	0.00	0.00	100.00	100.00
68	Koteswara Rao	0.00	0.00	0.00	0.00	100.00
68	Krishan Kant Mangla	0.00	0.00	0.00	0.00	100.00
68	Raj Dosi	0.00	0.00	0.00	0.00	100.00
68	Shubham Kumar	0.00	0.00	0.00	0.00	100.00

Editorials - C For Code 02 - Coding Club - ISM Dhanbad

Cartman Reverses String 200 pts

Difficulty Level: Cake Walk

Just take the input in a string (character array), find the no. of elements in the string and start printing character by character from the end of the string.

Here is the code for the problem:

http://www.codechef.com/viewplaintext/2405460

Raise the Power 300 pts

Difficulty Level: Easy

Prerequisite: Divide and Conquer, Modular Arithmetic

If you are not acquainted with basic modular arithmetic, I recommend you to read basic number theory. Here are some modular arithmetic properties that are used here:

(A*B) mod M = (A mod M) * (B mod M)

(A^B) mod M = (A mod M) ^ B

Now since A can be as large as 10^18, we first take A=A mod (1,000,000,007).

Let me show the algorithm for solving A^B if B is very large with an example.

Let A = 3 and B = 18.

3^18 = (3^9) * (3^9)

3^9 = 3 * (3^4) * (3^4)

3^4 = (3^2) * (3^2)

3^2 = 3 * 3

So, we calculated 3^18 in just 4 steps. In this manner we can calculate A^B in O(log B).

Here is the code for this problem:

http://www.codechef.com/viewplaintext/2405463

How to Handle the Fans 500 pts

Difficulty Level: Medium

Prerequisite: Binary Indexed Tree

Binary Indexed Tree is a data structure that is used to calculate the cumulative frequency. If we use an array to store the no. of fans at each point and then count them one by one, the time complexity will become O(N*Q) and it will give TLE.

Binary Indexed Tree allow us to update the no. of fans at each point and count the no. of fans from office A to B in log N steps. So the time complexity of algorithm will be O(Q * log N), this will work fine.

To read about Binary Indexed Trees, please read this:

http://community.topcoder.com/tc?module=Static&d1=tutorials&d2=binaryIndexedTrees

Here is the solution for this problem:

http://www.codechef.com/viewplaintext/2405466

Here is the Rank List for the Series "C For Code" after the first contest. Problem 1 was for 200 points, Problem 2 was for 350 points and Problem 3 for 450 points. 

Rank	Name	Problem 1	Problem 2	Problem 3	Total
1	Vaibhav Sethi	196.87	264.12	396.67	857.66
2	Vijay Tripathi	168.35	277.05	408.75	854.15
3	Karan Khullar	179.78	277.21	386.92	843.91
4	Gourav Pathak	163.69	296.79	360.00	820.47
5	Amit Jain	195.22	175.00	377.83	748.06
6	Abhinav Saraswat	196.50	0.00	366.21	562.71
7	Anuj Kumar	194.24	350.00	0.00	544.24
8	Sumit Awasthi	157.26	0.00	364.08	521.34
9	Mayank Yadav	197.54	245.84	0.00	443.38
10	Ashish Ranjan	198.00	230.51	0.00	428.51
11	Inderjeet Yadav	151.00	265.97	0.00	416.97
12	Vishesh Srivastava	195.61	197.46	0.00	393.07
13	Law Kumar	200.00	175.00	0.00	375.00
14	Prakhar Rastogi	187.65	175.00	0.00	362.65
15	Siddharth Behera	186.04	175.00	0.00	361.04
16	Prakhar Rastogi	179.11	175.00	0.00	354.11
17	Aman Jain	0.00	0.00	228.00	228.00
18	Jayant Tiwari	197.83	0.00	0.00	197.83
19	Rohit Kumar	197.44	0.00	0.00	197.44
20	Anuj Asher	197.17	0.00	0.00	197.17
21	Prateek Kumar Nischal	196.81	0.00	0.00	196.81
22	Rohit Kumar	195.46	0.00	0.00	195.46
23	Nitish Gupta	195.02	0.00	0.00	195.02
24	Yogendra Singh Vimal	194.61	0.00	0.00	194.61
25	Robin Parashar	194.30	0.00	0.00	194.30
26	Sujay Raj	190.00	0.00	0.00	190.00
27	Anil Bakhla	188.72	0.00	0.00	188.72
28	Sakshi Gopal	188.15	0.00	0.00	188.15
29	Ashish Awasthi	186.43	0.00	0.00	186.43
30	Anjaney Pandey	183.00	0.00	0.00	183.00
31	Saurabh Prasad	175.17	0.00	0.00	175.17
32	Ashawani Chandil	172.54	0.00	0.00	172.54
33	Anant Kumar	169.24	0.00	0.00	169.24
34	Saurav Kothari	166.50	0.00	0.00	166.50
35	Pawan Deshmuch	163.89	0.00	0.00	163.89
36	Gayathri Devi	157.85	0.00	0.00	157.85
37	Niraj Kumar	148.98	0.00	0.00	148.98
38	Ashish Bahukhandi	147.98	0.00	0.00	147.98
39	Ravi Gupta	145.93	0.00	0.00	145.93
40	Nikhil Dubey	141.83	0.00	0.00	141.83
41	Mohit Srivastava	139.02	0.00	0.00	139.02
42	Deep Kumar Sakre	137.04	0.00	0.00	137.04
43	Arup Das	136.81	0.00	0.00	136.81
44	Prakash Tripathi	133.02	0.00	0.00	133.02
45	Pavan Kriplani	125.59	0.00	0.00	125.59
46	Ankur Agrawal	123.41	0.00	0.00	123.41
47	Akshay Agrawal	100.00	0.00	0.00	100.00
47	Anil Yadav	100.00	0.00	0.00	100.00
47	Anish Somani	100.00	0.00	0.00	100.00
47	Deepak Gupta	100.00	0.00	0.00	100.00
47	Hitesh Sharma	100.00	0.00	0.00	100.00
47	Koteswara Rao	100.00	0.00	0.00	100.00
47	Krishna Kumar Meena	100.00	0.00	0.00	100.00
47	Rahul Kumar Yadav	100.00	0.00	0.00	100.00
47	Raj Dosi	100.00	0.00	0.00	100.00
47	Shubham Kumar	100.00	0.00	0.00	100.00
47	Sravan Kumar	100.00	0.00	0.00	100.00
47	Swapnil Gupta	100.00	0.00	0.00	100.00

Editorials - C For Code 01 - Coding Club - ISM Dhanbad

Problem: Easy One For Cartman

This problem was a cakewalk. We know the first term A, second term B and the no. of terms N. So common difference is D=B-A.

Formula for sum of A.P. is
Sum = ( N * ( 2 * A + (N-1) * D ) ) / 2

So, Here is the code for this problem:

http://www.codechef.com/viewplaintext/2388336




Problem: Butters Counting Problem

Prerequisite: Binary Search.

Ok, for the beginners just assume that a computer can perform around 10^8 operations per second. From this you will get an idea of Time Limit. Time Limit for this problem was 1 second.
There were "Q" queries and "N" numbers. If you perform a linear search for every query, the time complexity will be O(Q * N)
Maximum possible value of Q * N is (10^5)*(10^5) i.e. 10^10, so this is for sure that this approach will give time limit exceeded.
On the other hand, if we perform Binary Search on the N numbers for each query, the time complexity will be O(Q * log N), its maximum value will be (10^5)*log(10^5), i.e. around 2 * 10^6, so it should run within the time limit.
So we have to use Binary Search here. Since the numbers are given in sorted order, we can directly perform binary search on it. We should search for the smallest element that is greater than "L" in the list. But there can be a case when such element does not exist, i.e. all the elements are less than or equal to "L". So we can make a separate code for this case, and all the other cases can be solved by binary search.

Here is the code for this problem:

http://www.codechef.com/viewplaintext/2389023

For more help on binary search you can read this tutorial:

http://community.topcoder.com/tc?module=Static&d1=tutorials&d2=binarySearch




Problem: Kyle Makes a List

Prerequisite: Longest Increasing Subsequence Problem, Dynamic Programming

if (x,y) and (a,b) are two consecutive pairs in the list then, y<a, also for every pair x<y and a<b
So, we conclude that x<a for every consecutive pairs. So our first step must be to sort the given pairs according to their first co-ordinate, and if first co-ordinates are same, then according to second co-ordinates.

After this we perform a variation of Longest Increasing Subsequence. A very nice explanation is given here:

http://www.geeksforgeeks.org/dynamic-programming-set-20-maximum-length-chain-of-pairs/

For Longest Increasing Subsequence Problem, read this:

http://www.geeksforgeeks.org/dynamic-programming-set-3-longest-increasing-subsequence/

Here is the solution to this problem: (I have used vectors and pairs in this solution, those who are not familiar with them, I recommend you to learn about vectors atleast as they are very powerful templates to solve problems easily on online algorithmic contests)

http://www.codechef.com/viewplaintext/2389120