Numbers from 1 to 1000, X per Line

[Austinomical]

Write a program which asks the user for a number X, and then outputs the numbers from 1 to 1000 , showing X numbers per line.

Use an integer for X, and validate user input...So, make sure the user only enters an X with a value between (10 to 30)

I have a few problems with my code to the above homework problem.
1) I can't get the validation to work
2) For my main loop for the problem, I don't know how to create a new line after X amount. The loop just runs in one continuous line. When it should look like this:

How many numbers per line would you like? 12

Numbers 1 - 1000, 12 per line:
1 2 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24

  #include <iostream>
#include <fstream>
using namespace std;

int main ()
{




    // Validation loop; user must enter a # from 10 - 30
    bool ok = false;
    int x;
    cout << "How many numbers per line would you like? " << endl;
    cin >> x;

    while (!ok)
    {
        cin >> x;

        if(!cin.fail() && (cin.peek()==EOF || cin.peek()=='\n'))
        {
            ok = true;
    }
    else
    {
        cin.clear();
        cin.ignore();
        cout << "Error, enter an integer between 10 and 30!" << endl;
    }

}

// Go here if user input is between 10 and 30
// Main Loop statement for x numbers per line until 1,000
    int x;
    cout << "How many numbers per line would you like? ";
    cin >> x;

    for(int i = 0; i < 1000; i++)
{
    cout << i << endl;
}










}
return 0;
}

[PrivateRyan]

http://www.cplusplus.com/doc/tutorial/operators/ - modulo operator

I think this might things much easier for you

[48T7M4Gy]

Why have you copied code from somewhere else instead of just writing something yourself and learning by trying and testing? Whoever gave it to you wasn't any help at all - that's the problem with quick fixes they usually take much longer than expected.

Lines 2, 11-32 have nothing to do with the question!

You need to be tidy too. Properly indent your code and get rid of all the blank lines.

Why didn't you compile your code?

Once you've tidied up your code and got rid of the rubbish you need to concentrate on lines 34-43.

Let us know how you get on so we can help with the validation. :)

[48T7M4Gy]

  #include <iostream>
  
  using namespace std;
  
  int main ()
  {
      int x;
      cout << "How many numbers per line would you like? ";
      cin >> x;
      
      for( int i = 0; i < 1000; i++ )
      {
        cout << i << ' ';
      }

    return 0;
}

[Austinomical]

The instructor gave us the first part of the code. I know it's not accurate but I don't know how to change it to make it fit into what I am doing. Just started coding last week so I have not learned proper format yet.

[48T7M4Gy]

Well all I can say is, if that is the complete question, then the code snippet given to you is bizarre.

Anyway all you have to do is use the code I posted and think carefully how you can use the value of X to get the desired number of items per line. Privates comment is one avenue.

The way to think about is first to consider how you would solve the problem using just pencil and paper.

[Austinomical]

I know what I want to do, but not sure how to do it. I know I just need to somehow make an if statement that tells the code to make a new line after X amount of numbers entered by the user

[48T7M4Gy]

So write the if statement down. You're on the right track. Have you run the program yet?

[Austinomical]

The only thing I can think to do would be to write

if (x == 10) {
cout << digits blah through blah
}

else if (x == 11) {
cout << digits blach through blah

etc..

Then maybe put this into its on loop? then put that inside the loop you made?

[E0p9LyTq]

Use the modulo operator (%) to print a newline:

#include <iostream>

int main ()
{
   std::cout << "How many numbers per line would you like? ";
   int x;
   std::cin >> x;

   for(int i = 1; i <= 1000; i++ )
   {
      std::cout << i << ' ';
      
      if (i % x == 0)
      {
         std::cout << '\n';
      }
   }
}

How many numbers per line would you like? 15
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 37 38 39 40 41 42 43 44 45
46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90
91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
106 107 108 109 110 111 112 113 114 115 116 117 118 119 120
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135
136 137 138 139 140 141 142 143 144 145 146 147 148 149 150
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165
166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210
211 212 213 214 215 216 217 218 219 220 221 222 223 224 225
226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
271 272 273 274 275 276 277 278 279 280 281 282 283 284 285
286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
301 302 303 304 305 306 307 308 309 310 311 312 313 314 315
316 317 318 319 320 321 322 323 324 325 326 327 328 329 330
331 332 333 334 335 336 337 338 339 340 341 342 343 344 345
346 347 348 349 350 351 352 353 354 355 356 357 358 359 360
361 362 363 364 365 366 367 368 369 370 371 372 373 374 375
376 377 378 379 380 381 382 383 384 385 386 387 388 389 390
391 392 393 394 395 396 397 398 399 400 401 402 403 404 405
406 407 408 409 410 411 412 413 414 415 416 417 418 419 420
421 422 423 424 425 426 427 428 429 430 431 432 433 434 435
436 437 438 439 440 441 442 443 444 445 446 447 448 449 450
451 452 453 454 455 456 457 458 459 460 461 462 463 464 465
466 467 468 469 470 471 472 473 474 475 476 477 478 479 480
481 482 483 484 485 486 487 488 489 490 491 492 493 494 495
496 497 498 499 500 501 502 503 504 505 506 507 508 509 510
511 512 513 514 515 516 517 518 519 520 521 522 523 524 525
526 527 528 529 530 531 532 533 534 535 536 537 538 539 540
541 542 543 544 545 546 547 548 549 550 551 552 553 554 555
556 557 558 559 560 561 562 563 564 565 566 567 568 569 570
571 572 573 574 575 576 577 578 579 580 581 582 583 584 585
586 587 588 589 590 591 592 593 594 595 596 597 598 599 600
601 602 603 604 605 606 607 608 609 610 611 612 613 614 615
616 617 618 619 620 621 622 623 624 625 626 627 628 629 630
631 632 633 634 635 636 637 638 639 640 641 642 643 644 645
646 647 648 649 650 651 652 653 654 655 656 657 658 659 660
661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
676 677 678 679 680 681 682 683 684 685 686 687 688 689 690
691 692 693 694 695 696 697 698 699 700 701 702 703 704 705
706 707 708 709 710 711 712 713 714 715 716 717 718 719 720
721 722 723 724 725 726 727 728 729 730 731 732 733 734 735
736 737 738 739 740 741 742 743 744 745 746 747 748 749 750
751 752 753 754 755 756 757 758 759 760 761 762 763 764 765
766 767 768 769 770 771 772 773 774 775 776 777 778 779 780
781 782 783 784 785 786 787 788 789 790 791 792 793 794 795
796 797 798 799 800 801 802 803 804 805 806 807 808 809 810
811 812 813 814 815 816 817 818 819 820 821 822 823 824 825
826 827 828 829 830 831 832 833 834 835 836 837 838 839 840
841 842 843 844 845 846 847 848 849 850 851 852 853 854 855
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870
871 872 873 874 875 876 877 878 879 880 881 882 883 884 885
886 887 888 889 890 891 892 893 894 895 896 897 898 899 900
901 902 903 904 905 906 907 908 909 910 911 912 913 914 915
916 917 918 919 920 921 922 923 924 925 926 927 928 929 930
931 932 933 934 935 936 937 938 939 940 941 942 943 944 945
946 947 948 949 950 951 952 953 954 955 956 957 958 959 960
961 962 963 964 965 966 967 968 969 970 971 972 973 974 975
976 977 978 979 980 981 982 983 984 985 986 987 988 989 990
991 992 993 994 995 996 997 998 999 1000

[keskiverto]

Use an integer for X, and validate user input...So, make sure the user only enters an X with a value between (10 to 30)

The "input validation" means that you check the input that it is of the type that you need.

int x;
std::cin >> x;

There are three possibilities after line 2:
1) User did not input integer. The stream is in an error state. The error has to be cleared before you can ask for integer again.
2) User did give integer, but not in valid range. You have to ask again.
3) The x holds a valid integer.

There has to be a loop that continues to ask again and again, until you do reach case 3. The cases 1 and 2 need different treatment.

[blazeking]

I'm also very new to C++, sounds like we're at the same point. Awesome!

Can't you run a WHILE loop after cin? Assuming cin is an integer, this might work if ran after the cin input:

while (x < 10 || x > 30)
    {
        cout << "Please enter a number between 10 and 30. ";
        cin >> x;
    }

[E0p9LyTq]

blazeking wrote:

Can't you run a WHILE loop after cin?

You could, a do-while would work as well.

do
{
   std::cout << "Please enter a number between 10 and 30: ";
   std::cin >> x;
} while (x < 10 || x > 30);

[48T7M4Gy]

You can also add an addition few lines to show the number entered is out of range too:

#include <stdio.h>
#include <iostream>

using namespace std;

int main ()
{
    // Validation loop; user must enter a # from 10 - 30
    bool ok = false;
    int x;
    int counter = 0;
    
    
    char prompt[] = "How many numbers per line would you like? ";
    
    cout << prompt;
    cin >> x;
    
    while (!ok || (x < 10 || x > 30) )
    {
        cout << prompt;
        cin >> x;
        
        if( !cin.fail() )
        {
            ok = true;
        }
        else
        {
            cin.clear();
            cin.ignore();
            cout << "Error, enter an integer between 10 and 30!" << endl;
        }
        
    }
    
    // Print table of values
    counter = 0;
    for(int i = 0; i < 1000; i++)
    {
        cout << i << ' ';
        counter++;
        
        if (counter % x == 0)
            std::cout << '\n';
    }
    
    std::cout << '\n';
    
    return 0;
}

[Half Life G Man]

@kemort

while (!ok || (x < 3 || x > 30))

Should be :

while (!ok || (x < 10 || x > 30))

cout << "Error, enter an integer between 10 and 30!" << endl;

[48T7M4Gy]

Yeah, you're right. I changed the values to save me counting up columns while testing and forgot to put them back the way the OP states. Well spotted Life/2

It's all fixed and the pond has gone back to a smooth surface.

[dhayden]

There are two hard parts to this problem: validating the input and printing the newlines.

Validating the input is a whole lot easier if you recognize that you can break out of the middle of a loop. Also, you can check whether cin (or any stream) is good by just saying if (cin) .... This is because streams have a built-in conversion to bool operator that returns whether the stream is good. Finally, I changed x to the more descriptive numPerLine. Here is your "prompt and validate" code with these changes:

    // Validation loop; user must enter a # from 10 - 30
    unsigned numPerLine;
    while (true) {
        cout << "How many numbers per line would you like? " << endl;
        cin >> numPerLine;
        if (cin) {
            break;   // input is good
        } else {
            cin.clear();
            cin.ignore();
            cout << "Error, enter an integer between 10 and 30!" << endl;
        }
    }

Note that this code doesn't check whether the number is between 10 and 30, but I think you can add that yourself.

As others have pointed out, the trick to printing the newlines is to keep a separate counter of some sort, but I would avoid the modulo operation in this case because it isn't necessary and division, which modulo requires, is time consuming. Also, you can avoid printing a space at the end of each line if you recognize that the counter determines whether you want to print a newline or a space:

    unsigned onThisLine = 0;    // numbers printed on current line
    for (unsigned x = 1; x <= 1000; ++x) {
        cout << x;
        if (++onThisLine == numPerLine) {
            cout << '\n';
            onThisLine = 0;
        } else {
            cout << ' ';
        }
    }