Tsuchiya Yoshihiro Blog

Project euler memo: Problem 383

2012-05-11T22:13:00.000+09:00

Problem 383: Divisibility by 5^x. It took too long to solve it. My program got messy, and this problem proved that I am not a good programmer. When I looked at the forum I found that everybody does much better and clean job. Less than 0.1 seconds in Python.

Project euler memo: Problem 360

2012-05-01T10:30:00.000+09:00

Problem 360: Scary sphere. You need to find all the lattice points on a large sphere. I had been thinking about this problem for a long time, and I am pleased to solve it. It takes 3.5 minutes in Python. I like this problem.
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(Update) I posted my code to the forum. After I cleaned the code, it runs faster than before. 2 minutes.

Project euler memo: Problem 364

2012-04-23T22:53:00.000+09:00

Problem 364: It's not very hard but I was not good at computing the number of combination. It took 75 minutes in C++, which is terrible. I am leaning something in the forum.
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(Update 04/24/2012)
I learned very efficient algorithm in the forum, and now it just one second in C++.

Project euler memo: Problem 381

2012-04-22T11:02:00.002+09:00

Problem 381: An easy problem. When I saw this problem it was one o'clock midnight and I saw people were finishing this problem very quickly. I tried but I could not solve it, so I was depressed and went to bed. When I see the problem in the morning, I felt it was easy. Four seconds in C++.

Project euler memo: Problem 337

2012-04-20T00:14:00.002+09:00

Problem 337: Totient sequence. After 378, I learned something, and I solved this one. It was still not straightforward for me. It took seven seconds in C++.

Congratulations, the answer you gave to problem 337 is correct.
You are the 227th person to have solved this problem.

Project euler memo: Problem 378

2012-04-04T21:24:00.003+09:00

Problem 378: Searching the size of sets: (i,j,k) such that dT(i) > dT(j) > dT(k). It seems that I need to learn a new algorithm. Some hours in Python. That's terrible.

Project euler memo: Problem 377

2012-03-26T19:23:00.000+09:00

Problem 377: It's an easy problem. However the example (n = 5) does not cover all the necessary case. I made a mistake on it, and it took little long to solve it. 30 seconds in Python. I was the 55th solver.

Project euler memo: Problem 236

2012-03-22T21:40:00.001+09:00

Problem 236: Luxury hamper. I almost brute forced it. 8 minutes and half in Python.
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(Update) I tired to find all the 35 answers. To search only the biggest one, it just takes 2 and half minutes.

Project euler memo: Problem 374

2012-03-18T22:44:00.000+09:00

Problem 374: "Maximum integer partition product". It's an interesting problem. I wrote a lots of lines of code. 2.5 seconds in C++. People in the forum are posting simpler codes. I will check those tomorrow.

Project euler memo: Problem 375

2012-03-13T19:59:00.000+09:00

Problem 375: Counting the sum of A[i,j] = min(range(i,j)) for a random sequence. I like this simple problem. 30 seconds in C++. I posted my code in the forum.

Project euler memo: Problem 248

2012-03-05T22:31:00.003+09:00

Problem 248: Finding numbers with totient 13!. It is a problem for programming rather than math. Three minutes in Python. I am sure I can optimize it.

I spent a day to debug it, but I'm happy I can go bed now.

Project euler memo: Problem 241

2012-03-03T22:26:00.001+09:00

Problem 241: The perfection quotient. Counting the number n such that sigma(n)/n = k + 1/2. I need to find a better way to do it since it took too long. 24 minutes in Python.

Project euler memo: Problem 163

2012-02-26T17:47:00.001+09:00

Problem 163: Counting number of triangles in triangles. Less than a second in Python.

Project euler memo: Problem 194

2012-02-26T00:37:00.001+09:00

Problem 194: The number of combination that box like graphs form. First, it looked hard, and I hadn't looked at this problem very long, but this time, I read the problem carefully and I understood what is required. One second and half in Python. There's one more problem that I left in 100s (163).

Project euler memo: Problem 371

2012-02-21T23:26:00.000+09:00

Problem 371: Lots of excuse that I could not solve it. I had been in San Jose for five days and it was a week trip from my home. You need to find the number of chance that n + m == 1000. Two seconds in Python.

Project euler memo: Problem 254

2012-02-08T23:24:00.001+09:00

Problem 254: I had difficulty to remember this problem. There are functions f, sf, g and sg. I tried to create inverse functions of g, sf and f. However this task is not straightforward. Five minutes in Python.

Project euler memo: Problem 237

2012-02-04T17:02:00.000+09:00

Problem 237: Tours on a 4xn board. First I had no idea to solve this problem, next I thought moves on each boxes, such as vertical, horizontal and L-shapes, but it was a sort of mess. Then I picked up a pen and thought about moves on each 4-box strips and found that there are just small number of moves, and I can avoid loops in the board. 20m seconds in C++.

Project euler memo: Problem 324

2012-01-20T21:11:00.000+09:00

Problem 324: Filling a very high tower (3x3x10^10000) with blocks (1x1x2). I first tried with something similar to problem 161. I found the correct, but it took too long to finish 10^1000: 4 hours with C++. I need to read the forum.
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(update) With a minor change, it takes 2 hours now.

Project euler memo: Problem 258

2012-01-09T17:36:00.000+09:00

Problem 258: Lagged Fibonacci sequence. I heard that it is used to generate random number sequences. It is also written that it has a long cycle, but I am not sure how long for the parameter of this problem. I had been trying to solve this problem in several wrong ways, but finally I got closer yesterday, but my implementation was very slow. From very early morning today, I had run my code four or five times in 3 hour interval, and got wrong answers. Finally I found a way with 30 minutes in C++ and a correct answer.

Project euler memo: Problem 365

2012-01-03T00:13:00.000+09:00

Problem 365: 'A huge binomial coefficient". I am glad that I finished this problem. Four and half minutes in Python. Also I am 100th person for this problem. Nice number for the new year. The message from Euler:

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Congratulations, the answer you gave to problem 365 is correct.

You are the 100th person to have solved this problem.

Nice work, tsuchiya.yoshihiro, you've just advanced to Level 13.
133 members (0.07%) have made it this far.

You have earned 1 new award:

High Flyer: Progress to the maximum level

Project euler memo: Problem 363

2011-12-23T00:59:00.001+09:00

Problem 363: Bézier curve. An easy problem. One and half minutes in Python.

Project euler memo: Problem 362

2011-12-18T11:24:00.001+09:00

Problem 362: Counting the number of square free factorization. I am the 50th person who solved this problem and this is the first time for me to get in to a fast solver list. It has been about a week since after the problem was published. Two minutes in C++.

Project euler memo: Problem 181

2011-11-24T18:59:00.001+09:00

Problem 181: Creating groups in Black and White objects. I took a simple method, however there was a bug to produce a dictionary ordered sequence. Thee minutes in Python.

Project euler memo: Problem 359

2011-11-21T23:02:00.001+09:00

Problem 359: Hilbert's infinite hotel. I do not like this non-natural way of introduction of the problem. First, I wrote a brute force. I do not quite understand why, but looking at the numbers, I found something and wrote a program in Python. 0.04 sec in Python.

Project euler memo: Problem 358

2011-11-19T13:27:00.001+09:00

Problem 358: After coming back from Munich, I finally recovered from jet lag. The problem is on the cyclic number. This is not very hard, but interesting. 14 minutes in Python. Is there any way to speed that up?