blob: 5d6235640f07f9ee33b1f21ec6b07e611edcf0e6 (
plain)
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
|
#include <stdlib.h>
#include <stdio.h>
void ComputePi(int numdigits, char* pi)
{
int alength = 10 * numdigits / 3;
int* a = (int*) malloc(alength * sizeof(int));
int piLength = 0;
int nines = 0;
int predigit = 0;
int i, j;
for(i = 0; i < alength; ++i)
a[i] = 2;
for (j = 0; j < numdigits; ++j)
{
int q = 0;
int p = 2 * alength - 1;
for (i = alength; --i >= 0; )
{
int x = 10*a[i] + q*(i+1);
a[i] = x % p;
q = x / p;
p -= 2;
}
a[0] = q % 10;
q /= 10;
if (q == 9)
++nines;
else if (q == 10)
{
int k;
pi[piLength] = (char) (predigit + 1 + '0');
for (k = 1; k <= nines; ++k)
pi[piLength+k] = '0';
piLength += nines + 1;
predigit = 0;
nines = 0;
}
else
{
int k;
pi[piLength] = (char)(predigit + '0');
predigit = q;
for (k = 1; k <= nines; ++k)
pi[piLength + k] = '9';
piLength += nines + 1;
nines = 0;
}
}
pi[piLength] = (char)(predigit + '0');
pi[piLength+1] = '\0';
free(a);
}
int main(int argc, char** argv)
{
int numdigits;
char* pi;
if (argc <= 1)
{
fprintf(stderr, "usage: pi #DIGITS [FILE]");
return 1;
}
numdigits = atoi(argv[1]);
pi = (char*) malloc(numdigits+1);
ComputePi(numdigits, pi);
if (argc > 2)
{
FILE* fp = fopen(argv[2], "w");
if (fp == NULL)
{
fprintf(stderr, "Cannot open %s\n", argv[2]);
return 2;
}
fputs(pi, fp);
fputc('\n', fp);
fclose(fp);
}
else
puts(pi);
free(pi);
return 0;
}
|
