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  1. #include<iostream>
  2. #include<stdlib.h>
  3. using namespace std;
  4.  
  5. int N=0;
  6. char* ptr;
  7.  
  8.  
  9. void gen_sieve_primes(void)
  10. {
  11.     for (int p=2; p<N; p++)
  12.     {
  13.         if(*(ptr+p) == '0')
  14.             *(ptr+p) = 'p';
  15.  
  16.  
  17.         int c=2;
  18.         int mul = p * c;
  19.         for(mul=p*c; mul < N;c++)
  20.         {
  21.             *(ptr+mul) = 'c';
  22.            // c++;
  23.             mul = p*c;
  24.         }
  25.     }
  26. }
  27.  
  28. void print_all_primes()
  29. {
  30.     int c = 0;
  31.     for(int i=0; i<N; i++)
  32.     {
  33.         if(*(ptr+i) == 'p')
  34.         {
  35.             c++;
  36.  
  37.             if(c < 4)
  38.             {
  39.                 switch(c){
  40.                 case 1:
  41.                     cout << c << "st prime is: " << i << endl;
  42.                     break;
  43.                 case 2:
  44.                     cout << c << "nd prime is: " << i << endl;
  45.                     break;
  46.                 case 3:
  47.                     cout << c << "rd prime is: " << i << endl;
  48.                     break;
  49.  
  50.                 default:
  51.                     break;
  52.                 }
  53.             }
  54.  
  55.             else
  56.                 cout << c << "th prime is: " << i << endl;
  57.         }
  58.     }
  59. }
  60.  
  61. int main()
  62. {
  63.  
  64.     cout<<"Enter the value of N:\n";
  65.     cin>>N;
  66.  
  67. ptr=(char*)calloc(N,sizeof(char));
  68.     int i;
  69.     for(i=0;i<N;i++)
  70.     {
  71.     *(ptr+i)='0';
  72.     }
  73.     gen_sieve_primes();
  74.  
  75.     print_all_primes();
  76.  
  77.     free(ptr);
  78.  
  79.     return 0;
  80. }
Success #stdin #stdout 0s 3032KB
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stdin
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1000
stdout
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Enter the value of N:
1st prime is: 2
2nd prime is: 3
3rd prime is: 5
4th prime is: 7
5th prime is: 11
6th prime is: 13
7th prime is: 17
8th prime is: 19
9th prime is: 23
10th prime is: 29
11th prime is: 31
12th prime is: 37
13th prime is: 41
14th prime is: 43
15th prime is: 47
16th prime is: 53
17th prime is: 59
18th prime is: 61
19th prime is: 67
20th prime is: 71
21th prime is: 73
22th prime is: 79
23th prime is: 83
24th prime is: 89
25th prime is: 97
26th prime is: 101
27th prime is: 103
28th prime is: 107
29th prime is: 109
30th prime is: 113
31th prime is: 127
32th prime is: 131
33th prime is: 137
34th prime is: 139
35th prime is: 149
36th prime is: 151
37th prime is: 157
38th prime is: 163
39th prime is: 167
40th prime is: 173
41th prime is: 179
42th prime is: 181
43th prime is: 191
44th prime is: 193
45th prime is: 197
46th prime is: 199
47th prime is: 211
48th prime is: 223
49th prime is: 227
50th prime is: 229
51th prime is: 233
52th prime is: 239
53th prime is: 241
54th prime is: 251
55th prime is: 257
56th prime is: 263
57th prime is: 269
58th prime is: 271
59th prime is: 277
60th prime is: 281
61th prime is: 283
62th prime is: 293
63th prime is: 307
64th prime is: 311
65th prime is: 313
66th prime is: 317
67th prime is: 331
68th prime is: 337
69th prime is: 347
70th prime is: 349
71th prime is: 353
72th prime is: 359
73th prime is: 367
74th prime is: 373
75th prime is: 379
76th prime is: 383
77th prime is: 389
78th prime is: 397
79th prime is: 401
80th prime is: 409
81th prime is: 419
82th prime is: 421
83th prime is: 431
84th prime is: 433
85th prime is: 439
86th prime is: 443
87th prime is: 449
88th prime is: 457
89th prime is: 461
90th prime is: 463
91th prime is: 467
92th prime is: 479
93th prime is: 487
94th prime is: 491
95th prime is: 499
96th prime is: 503
97th prime is: 509
98th prime is: 521
99th prime is: 523
100th prime is: 541
101th prime is: 547
102th prime is: 557
103th prime is: 563
104th prime is: 569
105th prime is: 571
106th prime is: 577
107th prime is: 587
108th prime is: 593
109th prime is: 599
110th prime is: 601
111th prime is: 607
112th prime is: 613
113th prime is: 617
114th prime is: 619
115th prime is: 631
116th prime is: 641
117th prime is: 643
118th prime is: 647
119th prime is: 653
120th prime is: 659
121th prime is: 661
122th prime is: 673
123th prime is: 677
124th prime is: 683
125th prime is: 691
126th prime is: 701
127th prime is: 709
128th prime is: 719
129th prime is: 727
130th prime is: 733
131th prime is: 739
132th prime is: 743
133th prime is: 751
134th prime is: 757
135th prime is: 761
136th prime is: 769
137th prime is: 773
138th prime is: 787
139th prime is: 797
140th prime is: 809
141th prime is: 811
142th prime is: 821
143th prime is: 823
144th prime is: 827
145th prime is: 829
146th prime is: 839
147th prime is: 853
148th prime is: 857
149th prime is: 859
150th prime is: 863
151th prime is: 877
152th prime is: 881
153th prime is: 883
154th prime is: 887
155th prime is: 907
156th prime is: 911
157th prime is: 919
158th prime is: 929
159th prime is: 937
160th prime is: 941
161th prime is: 947
162th prime is: 953
163th prime is: 967
164th prime is: 971
165th prime is: 977
166th prime is: 983
167th prime is: 991
168th prime is: 997
https://ideone.com/qAGto3
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
secret

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