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### 10198 Counting

Posted: Wed May 21, 2003 12:30 pm
Can anyone tell me how to solve this?

Posted: Sat May 24, 2003 6:47 am
It's not too hard to see the recurrence relations.. and once you got that, you can easily solve it using DP...

This is like a really simple textbook counting example. It extends how you would do fib sequence.. so maybe you should consult a textbook or online... if you still have no idea, feel free to message me..

Posted: Tue May 27, 2003 6:22 am
It's not too hard to see the recurrence relations.. and once you got that, you can easily solve it using DP...
Please tell me more about the recurrence relations. I can't find it.

Posted: Tue May 27, 2003 10:06 pm
Well, these numbers very similar to Fibonacci numbers, but they are not the same. So the recurence is
f[1]:=2;
f[2]:=5;
f[3]:=13;
f[n]:=2*f[n-1]+f[n-2]+f[n-3];

Posted: Wed May 28, 2003 8:20 am
Could you tell me how you get this recurency ?
I try to find this recurrency , but I fails ... and I think about more complicated version of this

Best regards
DM

Posted: Sat Aug 02, 2003 3:55 am
This might be a little late, but i just thought i'll try and explain his algo..
let f(n) denote the no of ways to make numbers with the sum n. The number of ways to make n is the same as the number of ways to make n-1 + no of ways to make n-2 + no of ways to make + no of ways to make n-3 + no of ways to make n-4. However since 4 = 1, it is basically

f(n) = 2 * f(n-1) + f(n-2) + f(n-3)

### 10198

Posted: Tue Sep 16, 2003 5:42 am
Well, I've got the recursion function going for this problem, and my formula works really well. I saved all the values of f(n) into an array which works out or the values of n >0 and n<1000 before the user inputs the number, so when n is called in the recursion function, it calls the array, array[n]. I found this method to be dramatically faster than calculating the value on-the-fly.

I'm still suffering problems. When I type in the number 999, the output number is something like 384 digits long. Because there are such large numbers, it takes a while for the computer to calculate every value for n.
How would I speed up my program. I don't know much about data structures, so any help/direction would be greatly appreciated. I always get time limit exceeded:(

I'm so close, but no cigar!

Thanks
GCS

### 10198 - Counting

Posted: Mon Oct 13, 2003 1:44 am
I'm trying to solve the problem n

### quick help

Posted: Thu Oct 23, 2003 9:50 pm
hey
use an array saveF[10001], to save already the computed values of f(k)

otherwise you compute the same values over and over, and it is veeeery slow

### big nubmers

Posted: Thu Oct 23, 2003 9:57 pm
also, there are going to be very big numbers (being 64 bit ) after k becomes 70-80

nick

### The recurrence of 10198

Posted: Fri Nov 28, 2003 4:59 pm
Hy Dmytro_Chernysh,

I would like to know if you got Accepted using this recurence:

f[1]:=2;
f[2]:=5;
f[3]:=13;
f[n]:=2*f[n-1]+f[n-2]+f[n-3].

I'm asking because I tried do use it, but I got WA.
Maybe, I am having problems like ravingavin. The numbers became very big and their representation can be done in a wrong way. My code is in C++. What can I do to solve this problem?

Besides that, I have a doubt:

when n=4, the output is 2 or 33?

And, can you send me some input examples?

Thanks,

Charlla

--------
My code is:

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
//#include<io.h>

unsigned long vetor_T[1000];

int cont;

void calcula()
{

vetor_T[0]=2;
vetor_T[1]=5;
vetor_T[2]=13;

while (cont<1000)
{

vetor_T[cont]=2*vetor_T[cont-1]+vetor_T[cont-2]+vetor_T[cont-3];
cont++;
}
}

int main()
{
int n;

cont=3;

calcula();

#ifndef ONLINE_JUDGE
close (0); open ("DATA.IN", O_RDONLY);
close (1); open ("DATA.OUT", O_WRONLY | O_CREAT, 0600);
#endif

while (scanf ("%d",&n)>0){

printf ("%lu\n", vetor_T[n-1]);

}
return 0;
}

And the numbers I tried (my input) are:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
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42
43
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45
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47
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49
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53
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181
182
183
184
185
186
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213
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221
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223
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921
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925
926
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928
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931
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933
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938
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941
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981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000

And output for those numbers were:
2
5
13
2
84
214
545
1388
3535
9003
22929
58396
148724
378773
964666
2456829
6257097
15935689
40585304
103363394
263247781
670444260
1707499695
53724135
2485392225
2437040984
3118231032
2568960681
2103258786
1303774693
2984801557
786702001
1567012956
2610562174
3279872009
2147384556
1595268703
27859379
3798372017
629937524
791139148
1715620541
557350458
3621460605
925957617
1735759001
3723968928
1519719882
4204200397
767187716
2963328415
2308110351
4051769537
490075952
3045064496
2042039889
3324252930
3145675653
3067709533
4015413057
1359309412
1211806822
3503368817
987919276
2396046895
693447291
475893457
4041281100
661968356
1546143973
3500570106
619317949
1990382681
3805686121
1631138280
468410770
2078678645
1961939044
2176000207
4097650807
3743306273
875361672
1001745832
2327192313
2236524834
3507020517
2987823589
3129257937
4163425388
1559030414
1820809561
774140332
633153343
3861256579
539872241
1279187108
2664535740
2853163533
1060115322
3342962621
2009269505
4126649657
720629552
3282210970
2821766557
1056439044
3921888319
3132047647
2652488065
3768977504
437588832
3001675937
1619983618
2384264709
800254381
1309789793
1509131380
833339638
190633153
2723737324
2176480143
2972363467
2255009809
1068928636
3070263252
874530357
1593285306
2836396925
3845642217
3531032073
859201400
505142498
1105551173
3575446244
171651567
729333255
910797025
2722578872
2790320728
624082761
2466097826
4051631845
2603509685
3134814449
39868540
1523093918
1925903529
1119802220
1393634591
1538007635
1294484785
1225644500
988814124
202790237
2620039098
2136715261
2801292561
1769404889
4181850304
49496170
1755280237
3446939652
108721119
1124694831
1510083137
4253582224
2552007824
2277746417
2771148290
1782116229
23192573
304682369
2414673540
862254726
148898065
3574724396
3865634287
2864956443
285369681
3006362796
573117124
142999429
3865478778
4152106813
3722757241
2578198185
146358536
2298705202
3026999829
4204096100
848995343
339152023
1436428193
4061003752
1307653128
3817770905
119296802
1069050341
1780201093
453782033
3756815500
1157679534
2230989305
786539052
666779647
56120355
1565559409
3854018820
739782812
2604176557
1212220154
1473432381
2468294177
3327273593
2006339152
1218311482
3475268413
1585252868
3569118335
3608823359
3782083329
1857206464
2515385024
2080125249
4237874690
186357765
2395748173
625794209
3833694356
2098996502
67546977
1772817516
1417211215
379819627
3949667985
1106432220
2247384756
960935125
980719930
874792445
3691239945
648057673
1567180440
3178691202
4277653221
416276196
3993929519
4091853863
4003978849
3208839192
1628609208
1880101865
7717538
3524146149
346177109
4224217905
3728824476
3438109374
1944359241
2465717740
1723969503
3563048691
2725850033
2148783668
1996531468
277762045
405871930
3086037373
2560741425
23457561
1398726624
1086684938
3595554061
1086585092
2560441887
1213088335
1778236353
3035035632
471461360
1461227409
2133984514
1905690501
3111625629
1672991681
4068332196
36379814
1519116209
2847977132
2956482991
1690124731
594774993
1541190412
1072313252
4280591909
2584752890
1932476349
2140362905
208020457
193912872
2736209106
1579384245
1793923172
3608472399
2000317623
813096225
2940015176
103509608
3960130617
2373851426
221408485
2481831717
3263956049
641217708
2733255886
781750937
643008172
506055871
2436870851
1727838449
2103636324
4077014652
3395569485
86888058
3351392957
1595308865
2333931449
1024630128
1683533274
2430660829
3274517764
2073295039
1261834079
3576513665
1898221856
44856864
1269481953
187075330
1688489477
538568941
2952702689
3837496500
2576330038
3352924673
234773996
2103835407
3500402187
749479185
2808228668
1276404116
1815548789
3420763066
1343544445
3628433449
3431239817
3244522936
663817250
3708429957
2735265508
1252843631
359448135
412038113
2436367992
1349254936
1251948681
1994552994
2295342309
3542218997
2784398705
2816424124
3369531358
3749950953
800955500
131458719
518856595
1970127409
295602836
3080189676
4131142301
3048142522
422715133
3729747793
2340418649
243365632
2261930410
2812677805
3835684356
4156042335
2075544943
3552881985
452449360
2238358352
4187080753
2475034626
2785573765
3643328317
3957330433
1458661060
1928046278
682149457
456038956
3522273647
3887768411
3163914833
852969836
167688324
57294021
1135246202
2495474749
1888522425
3112798505
2019659592
450705522
1738901845
1653201508
1201043087
1499222231
1557721761
1520741544
1803459784
2390415577
3810065186
3224071141
4058688453
2266611345
3226047692
4187460590
982678329
788930348
2453032319
2382706019
3712407409
3670618564
551448668
4190956013
4014044666
4180559421
3681217633
2672137465
321150096
2700687994
4099696253
2631296004
3473041663
792173695
3393717761
2462716288
521389440
2604245633
3897629698
2330959877
2573860493
2786375969
1887637716
545577302
1470200993
1078649708
4173077711
2305071531
1271935889
432086428
146212980
1996448277
276228666
2695118589
3367946825
1117306313
4002710744
3900740034
36595237
3681673956
2710748591
549831783
3197118817
1064883416
1581750136
3130535209
317769378
1052856805
1259050901
3888727985
1499429084
3851669758
206594697
1469320940
2701939039
2784826419
1150978225
3493754612
2333379276
721556797
2975280186
415561853
232993393
3856828825
4067245600
3634378826
2307930189
3727550212
512507551
2765528207
1181179585
1345427632
2342595760
2916831441
931751682
2827963269
914575069
1293897793
2035366628
1984238822
3002774769
1435220396
3562487087
2973034747
2353842385
2653272012
2043486564
504152933
1410097146
1072866493
4059983065
2012995177
568905320
2915821586
4118576373
3131945060
413386191
3782326519
2520049697
645877512
3299163944
1174320505
1998715170
4175947493
2934996069
3454720209
1135482092
70745870
436726745
2079681452
371868223
3260144643
381904369
100854308
3843757628
3875306637
3105290618
1044743613
480149889
815366713
3155626928
3311803162
2004665373
1886826244
500186431
596897183
3580807041
3963730400
3515230432
1690096417
2269219074
1153830405
1972009005
3072100193
680105204
2109352310
3675942721
1551408364
298177167
1528738123
612094481
3051104252
3948073812
2969411765
53099706
2728717693
4184979561
2561841929
3447446520
756812642
3227946437
2070217444
3830226671
73715335
1752907489
3114789688
3761234904
3800232393
1591587490
2154707685
1111300661
1673929201
2318899452
3128061470
1659017001
175060332
842231839
3518541011
3759406897
3289652052
972350124
403824605
774684090
2925542909
2734627217
579546841
2524296512
4067799786
2649508333
3301178372
434762975
2525245359
196497473
3353003280
837814800
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4250330522

### Re: big nubmers

Posted: Fri Nov 28, 2003 5:04 pm
Hey,

How can I solve this problem??? I mean, what can I do when, after k becomes 70-80, and the numbers become very big (being 64 bit )????

Thanks,

Charla
--------------

My code is:

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include<io.h>

unsigned long vetor_T[1000];

int cont;

void calcula()
{

vetor_T[0]=2;
vetor_T[1]=5;
vetor_T[2]=13;

while (cont<1000)
{

vetor_T[cont]=2*vetor_T[cont-1]+vetor_T[cont-2]+vetor_T[cont-3];
cont++;
}
}

int main()
{
int n;

cont=3;

calcula();

#ifndef ONLINE_JUDGE
close (0); open ("DATA.IN", O_RDONLY);
close (1); open ("DATA.OUT", O_WRONLY | O_CREAT, 0600);
#endif

while (scanf ("%d",&n)>0){
printf ("%lu\n", vetor_T[n-1]);

}
return 0;
}

Posted: Fri Nov 28, 2003 5:50 pm
Hi Charlla,

You do have a mistake -- you should have used "long arigfmetic" instead of just long long. For example, n=30
1186714748389

Obviously, for n=1000 the number is really huge

Hope you understood

Posted: Sat Nov 29, 2003 12:20 pm
Simple!

Use big integer.

Posted: Sat Nov 29, 2003 3:44 pm
Hey!

How can I represent this big integer in C???

Thanks,

Charla.
---------------------
sohel wrote:Simple!

Use big integer.