হ য ব র ল: Beginners Problems Light OJ Hints

1.
1000 - Greetings from LightOJ

Add a and b then print the result.

2.
1001 - Opposite Task

If n is less then 10 then print 0 and n. Else print n-10 and 10.

3.
1006 - Hex-a-bonacci

Do memorization or build tabulation form.

4.
1008 - Fibsieve`s Fantabulous Birthday

There is a pattern. We have to find the odd and even square number and the mid point of two square number. Then follow the pattern.

5.
1010 - Knights in Chessboard

Maximum number of knights that can be placed in the board considering the restrictions by giving place all knights either in white or in black squares.
That's mean K_nm = ½ * n * m [ if n*m is even] or K_nm = (½ * n * m) + 1 [if n*m is odd].
There is some special case for n = 1 or m = 1 and n = 2 or m = 2.

6.
1015 - Brush (I)

Print the summation of nonzero positive integers.

7.
1022 - Circle in Square

Find (Area of square - Area of Circle).

8.
1042 - Secret Origins

See this

9.
1045 - Digits of Factorial

Find digit of factorials by f[i] = log(i) + f[i-1], where i = 1 to 1000000, then answer will be floor(f[n]/log(base)) + 1.

10.

1053 - Higher Math

Apply a² + b² = c² [Pythagoras Theorem]

11.

1069 - Lift

Check between your position and lift's position then calculate the time.

12.

1072 - Calm Down

There is a large circle with radius R and n little circles each having radius r, are placed inside on the border of the large circle.

then, r = (R * sin(angle)) / (1+sin(angle))   where, angle = PI / n.

There is a large circle with radius R and n little circles each having radius r, are placed outside on the border of the large circle.

then, r = (R * sin(angle)) / (1-sin(angle))    where, angle = PI / n.

13.

1107 - How Cow

Determine if x is in the range of [x₁,x₂] and y is in the range of [y₁,y₂].

14.

1109 - False Ordering

First find the divisors of each number 1 to 1000, then place them in an array according to the condition. We have to pre-calculate the whole process. To do it a thing we have to keep in mind that no number will have more than √(1000) = 32 divisors.

15.

1113 - Discover the Web

We will use concept of stack in this problem. Take two stacks (use STL) and do whatever is said in the problem.

16.

1116 - Ekka Dokka

We have to find a number x such that W%(2^x)==0 and N = (W / x) should be odd. x should be in 1 to 63.

17.

1133 - Array Simulation

Do the operations using simple for loops.

18.

1136 - Division by 3

Let, a positive number sequence is -
1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17...
Now digit sum from 1 to N is (N*(N+1))/2.
for N = 1, digit sum = 1 % 3 = 1 (Not the result)
      N = 2,      "         = 3 % 3 = 0
      N = 3,      "         = 6 % 3 = 0
      N = 4,      "         = 10%3 = 1 (Not the result)
      .
      .
      .
Now, you will get a sequence where you can get a result.

19.

1182 - Parity

Use __builtin_popcount(n)function. 

20.

1189 - Sum of Factorials

First pre-calculate Sum of factorials - sum[i] = sum[i-1] + fact[i], where i is 1 to 20.
Then you can't get the result (or impossible) if (sum[pos] < n && fact[pos+1] > n)here pos is the position where (f[i]<=n). Now just print the result.

21.

1202 - Bishops

We have to think about 2 cases.

If there is a bishop in black cell and another one is in white cell the we can never take one bishop to other.
If both are in same color cells then we have to check whether they are in diagonally same position or not. If they are in diagonally same position then the result will be 1 otherwise 2.

22.

1211 - Intersection of Cubes

[Removed from beginner category in New LOJ version.]

23.

1212 - Double Ended Queue

Use STL deque<int>Q .

24.

1214 - Large Division

In JAVA you can easily solve this by BigInteger. In C/C++ use string to solve this problem.

25.

1216 - Juice in the Glass

Now, there is a angle, so, we can write-

_{r₁/(h+x) = r₂/x}
_{so, x = (hr₂)/(r₁-r₂)}

_{again, r/(p+x) = r₂/x}
_{[putting the value of x]}
_{so, r = ((p(r₁-r₂))/h) + r₂}

_{_{thus, V = (PI * p * (r² + r₂² + (r*r₂)))/3}}

_26.

_{1225 - Palindromic Numbers (II)}

_{Check the string from the end with the beginning. If it is not same then print No.}

_27.

_{1227 - Boiled Eggs}

_{No hints.}

_28.

_{1241 - Pinocchio}

_{First we will take a = 2 then we will check each value with a. If (a != value) then}_{cnt+=(ceil((value-a)/5))and set a = value.}

_29.

_{1249 - Chocolate Thief}

Each student will have exactly (total volume / n) volume chocolate. Now we will check which student has extra and which student has less than this value.

30.

1294 - Positive Negative Sign

Isn't it (n * m) / 2 ?? Try yourself... :p

31.

1305 - Area of a Parallelogram

Lets, O is the intersection point of AC & BD and it is also the mid point of AC & BD. So,

(Ax + Cx) / 2 = (Bx + Dx) / 2

or, Dx = Ax + Cx - Bx

similarly, Dy = Ay + Cy - By

Now, Using Shoelace Formula we can easily get the area.

32.

1311 - Unlucky Bird