pi_Machin_like_formula.cpp

#include <stdio.h>
#include <iostream>
using namespace std;
int main(void)
{ //本程序每四位数输出，如果请求计算的位数不是4的整数倍，最后输出可能会少1~3位数
	long a[2] = {956, 80}, b[2] = {57121, 25}, i = 0, j, k, p, q, r, s = 2, t, u, v, N, M = 10000;
	printf("%9cMachin%6cpi=16arctan(1/5)-4arctan(1/239)\nPlease input a number.\n", 32, 32);
	cin >> N, N = N / 4 + 3;
	long *pi = new long[N], *e = new long[N];
	while (i < N)
		pi[i++] = 0;
	while (--s + 1)
	{
		for (*e = a[k = s], i = N; --i;)
			e[i] = 0;
		for (q = 1; j = i - 1, i < N; e[i] ? 0 : ++i, q += 2, k = !k)
			for (r = v = 0; ++j < N; pi[j] += k ? u : -u)
				u = (t = v * M + (e[j] = (p = r * M + e[j]) / b[s])) / q, r = p % b[s], v = t % q;
	}
	while (--i)
		(pi[i] = (t = pi[i] + s) % M) < 0 ? pi[i] += M, s = t / M - 1 : s = t / M;
	for (cout << "3."; ++i < N - 2;)
		printf("%04ld", pi[i]);
	delete[] pi, delete[] e, cin.ignore(), cin.ignore();
	return 0;
}