98 lines
2.4 KiB
Rust
98 lines
2.4 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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extern crate num;
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use std::from_str::FromStr;
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use std::num::One;
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use std::num::Zero;
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use std::num::FromPrimitive;
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use num::Integer;
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use num::bigint::BigInt;
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struct Context {
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numer: BigInt,
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accum: BigInt,
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denom: BigInt,
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}
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impl Context {
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fn new() -> Context {
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Context {
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numer: One::one(),
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accum: Zero::zero(),
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denom: One::one(),
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}
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}
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fn from_int(i: int) -> BigInt {
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FromPrimitive::from_int(i).unwrap()
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}
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fn extract_digit(&self) -> int {
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if self.numer > self.accum {return -1;}
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let (q, r) =
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(self.numer * Context::from_int(3) + self.accum)
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.div_rem(&self.denom);
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if r + self.numer >= self.denom {return -1;}
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q.to_int().unwrap()
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}
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fn next_term(&mut self, k: int) {
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let y2 = Context::from_int(k * 2 + 1);
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self.accum = (self.accum + (self.numer << 1)) * y2;
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self.numer = self.numer * Context::from_int(k);
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self.denom = self.denom * y2;
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}
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fn eliminate_digit(&mut self, d: int) {
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let d = Context::from_int(d);
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let ten = Context::from_int(10);
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self.accum = (self.accum - self.denom * d) * ten;
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self.numer = self.numer * ten;
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}
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}
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fn pidigits(n: int) {
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let mut k = 0;
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let mut context = Context::new();
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for i in range(1, n + 1) {
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let mut d;
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loop {
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k += 1;
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context.next_term(k);
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d = context.extract_digit();
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if d != -1 {break;}
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}
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print!("{}", d);
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if i % 10 == 0 {print!("\t:{}\n", i);}
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context.eliminate_digit(d);
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}
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let m = n % 10;
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if m != 0 {
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for _ in range(m, 10) { print!(" "); }
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print!("\t:{}\n", n);
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}
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}
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fn main() {
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let args = std::os::args();
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let n = if args.len() < 2 {
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512
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} else {
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FromStr::from_str(args[1]).unwrap()
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};
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pidigits(n);
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}
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