第27回 オフラインリアルタイムどう書くの問題「分岐と行き止まり」をRustで解く ref: http://qiita.com/uehaj/items/25caa06ce666fc175d99

file0.txt

/*
http://nabetani.sakura.ne.jp/hena/ord27raswi/
*/
#![feature(collections)]
#![feature(core)]

extern crate core;
use std::string::String;
use std::collections::BTreeSet;
use core::iter::FromIterator;

static PATHS:[(char, char);21]
    = [('1','a'),('1','g'),('2','d'),('2','h'),
       ('3','b'),('3','f'),('a','b'),('b','5'),
       ('b','c'),('c','4'),('c','6'),('d','c'),
       ('d','e'),('e','5'),('f','g'),('g','c'),
       ('g','e'),('g','h'),('h','4'),('h','i'),
       ('i','6')];

fn traverse(node:char, stopper:&str) -> Vec<String> {
    if stopper.contains(node) {
        vec![]
    }
    else if node == '4' || node == '5' || node == '6' {
        vec![format!("{}", node)]
    }
    else {
        PATHS
            .iter()
            .filter(|&&(beg,_)|{beg==node})
            .flat_map(|&(_,end)|traverse(end, stopper).into_iter())
            .collect()
    }
}

fn solve(stopper:&str) -> Vec<String> {
    BTreeSet::from_iter(
        ['1','2','3']
            .iter()
            .flat_map(|start_point|
                      traverse(*start_point, stopper)
                      .iter()
                      .map(|end_point| format!("{}{}", *start_point, end_point))
                      .collect::<Vec<String>>()
                      .into_iter()
                      )).into_iter().collect::<Vec<String>>()
}

fn test(stopper: &str, expected: &str) {
    let mut answer = solve(stopper)
        .iter()
        .map(|s| s.as_slice())
        .collect::<Vec<&str>>().connect(",");
    if answer == "" {
        answer = String::from_str("-");
    }
    assert_eq!(answer, expected);
}

fn main() {
/*0*/ test( "befi", "14,16,24,26" );    
/*1*/ test( "abc", "14,15,16,24,25,26,34,35,36" );    
/*2*/ test( "de", "14,15,16,24,26,34,35,36" );    
/*3*/ test( "fghi", "14,15,16,24,25,26,34,35,36" );    
/*4*/ test( "abcdefghi", "-" );    
/*5*/ test( "ag", "24,25,26,34,35,36" );    
/*6*/ test( "dh", "14,15,16,34,35,36" );    
/*7*/ test( "bf", "14,15,16,24,25,26" );    
/*8*/ test( "ch", "15,25,35" );    
/*9*/ test( "be", "14,16,24,26,34,36" );    
/*10*/ test( "ci", "14,15,24,25,34,35" );    
/*11*/ test( "cgi", "15,24,25,35" );    
/*12*/ test( "acgi", "24,25,35" );    
/*13*/ test( "cdefghi", "15,35" );    
/*14*/ test( "acdefghi", "35" );    
/*15*/ test( "cdegi", "15,24,35" );    
/*16*/ test( "bcdegi", "24" );    
/*17*/ test( "afh", "14,15,16,24,25,26,34,35,36" );    
/*18*/ test( "abfh", "14,15,16,24,25,26" );    
/*19*/ test( "dfh", "14,15,16,34,35,36" );    
/*20*/ test( "cdfh", "15,35" );    
/*21*/ test( "deh", "14,15,16,34,35,36" );    
/*22*/ test( "cdeh", "15,35" );    
/*23*/ test( "abefgh", "24,26" );    
/*24*/ test( "abdefgh", "-" );    
/*25*/ test( "acfghi", "25,35" );    
/*26*/ test( "acdfghi", "35" );    
/*27*/ test( "cegi", "15,24,35" );    
/*28*/ test( "abcfhi", "15,25" );    
/*29*/ test( "abcefhi", "-" );    
/*30*/ test( "abdi", "14,15,16,24,34,35,36" );    
/*31*/ test( "abdfi", "14,15,16,24" );    
/*32*/ test( "bdi", "14,15,16,24,34,35,36" );    
/*33*/ test( "bdfi", "14,15,16,24" );    
/*34*/ test( "adfh", "14,15,16,34,35,36" );    
/*35*/ test( "adfgh", "34,35,36" );    
/*36*/ test( "acdfhi", "15,35" );    
/*37*/ test( "bcdfgi", "24" );    
/*38*/ test( "bcdfghi", "-" );    
/*39*/ test( "defi", "14,15,16,24,34,35,36" );    
/*40*/ test( "defhi", "14,15,16,34,35,36" );    
/*41*/ test( "cdefg", "15,24,26,35" );    
/*42*/ test( "cdefgi", "15,24,35" );    
/*43*/ test( "bdefg", "24,26" );    
/*44*/ test( "bdefgi", "24" );    
}