Submission #20432101

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Source Code Expand

// https://atcoder.jp/contests/arc113/tasks/arc113_e
//
#![allow(unused_imports)]
use std::io::*;
use std::io::Write;
use std::fmt::*;
use std::str::*;
use std::cmp::*;
use std::collections::*;

// Input macros.
// Original by tanakh: https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[allow(unused_macros)]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };

    ($iter:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };

    ($iter:expr, [ next / $t:tt ]) => {
        {
            let len = read_value!($iter, usize);
            (0..len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
        }
    };

    ($iter:expr, switch) => {
        {
            let ty = read_value!($iter, i32);
            if ty == 1 {
                vec![ty, read_value!($iter, i32), read_value!($iter, i32)]
            } else if ty == 2 {
                vec![ty, read_value!($iter, i32)]
            } else {
                vec![ty, read_value!($iter, i32)]
            }
        }
    };

    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };

    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };

    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

#[allow(unused_macros)]
macro_rules! read_line {
    ($t:tt) => {
        {
            let mut s = String::new();
            std::io::stdin().read_line(&mut s).unwrap();
            s.trim_right().parse::<$t>().unwrap()
        }
    }
}

#[allow(unused_macros)]
macro_rules! dvec {
    ($t:expr ; $len:expr) => {
        vec![$t; $len]
    };

    ($t:expr ; $len:expr, $($rest:expr),*) => {
        vec![dvec!($t; $($rest),*); $len]
    };
}

#[allow(unused_macros)]
macro_rules! ifv {
    ($t:expr, $a:expr, $b: expr) => {
        if $t { $a } else { $b }
    }
}

#[allow(unused_macros)]
macro_rules! fill {
    ($t:expr, $v:expr) => {
        for i in 0..$t.len() {
            $t[i] = $v;
        }
    };
}

#[allow(unused_macros)]
macro_rules! join {
    ($t:expr, $glue:expr) => {
        $t.into_iter().map(|w| w.to_string()).collect::<Vec<_>>().join($glue)
    };
}

#[allow(unused_macros)]
macro_rules! debug {
    ($($a:expr),*) => {
        eprintln!(concat!($(stringify!($a), " = {:?}, "),*), $($a),*);
    }
}

// ===

fn solve(query: Vec<char>) -> Vec<char> {
    let n = query.len();

    let mut an = 0;
    let mut cont_an = 0;
    let mut a_grp = vec![];
    for i in 0..n {
        if query[i] == 'a' {
            an += 1;
            cont_an += 1;
        } else {
            if cont_an >= 1 {
                a_grp.push((cont_an, i-cont_an));
                cont_an = 0;
            }
        }
    }
    if cont_an >= 1 {
        a_grp.push((cont_an, n-cont_an-1));
    }
    if an == n {
        return vec!['a'; n];
    }

    let mut tail_a = 0;
    for i in (0..n).rev() {
        if query[i] == 'a' {
            tail_a += 1;
        } else {
            break;
        }
    }
    let mut head_a = 0;
    for i in 0..n {
        if query[i] == 'a' {
            head_a += 1;
        } else {
            break;
        }
    }
    let mut ret = vec!['b'; n-an];
    // must not delete 'b'
    if tail_a >= 1 {
        let mut append = 0;
        let mut glue = 0;
        for &(c, pos) in &a_grp {
            if c >= 2 {
                append += c;
                glue += 1;
            }
        }
        if tail_a == 1 {
            append += 1;
            glue += 1;
        }
        if append % 2 != an % 2 {
            append += 1;
            glue += 1;
        }
        append -= 2 * (glue - 1);
        for i in 0..append {
            ret.push('a');
        }
        return ret;
    }

    if an % 2 == 0 {
        return vec!['b'; n-an];
    } else {
        if head_a == an {
            let mut ret = vec!['b'; 1+(n-an)];
            ret[0] = 'a';
            return ret;
        }
        if n >= 2 && query[n-2] == 'a' {
            let mut ret = vec!['b'; 1+(n-an)];
            let rn = ret.len();
            ret[rn-2] = 'a';
            return ret;
        }
        if n >= 3 && query[n-3] == 'a' {
            let mut ret = vec!['b'; 1+(n-an)];
            let rn = ret.len();
            ret[rn-3] = 'a';
            return ret;
        }

        let mut best = (0, 0);
        for &(c, pos) in &a_grp {
            if pos != 0 && best.0 < c {
                best = (c, pos);
            }
        }
        // debug!(query, a_grp, best);
        assert!(best.0 >= 1 && query[best.1-1] == 'b');
        let last_a = best.1;
        assert!(last_a >= 1);
        let mut q2 = vec!['-'; n-2];
        for i in 0..last_a-1 {
            q2[i] = query[i];
        }


        let mut w = last_a-1;
        for i in (last_a..n-1).rev() {
            q2[w] = query[i];
            w += 1;
        }
        assert!(w == n-2);
        return solve(q2);


        // bbbbbbbbbbbbbbbbbbaaa
        // bbbbbbbbbbbbbbbbbba
        // bbbaaabbbabbbabbbabbabbbb
        //                     ^       ^
        // bbbbbbbbbbbbbbbbbbaaa

        //
        // vec!['-'; n]
    }
}

fn main() {
    input! {
        t: usize,
        testcases: [chars; t]
    };


    for query in testcases {
        println!("{}", join!(solve(query), ""));
    }
}

Submission Info

Compile Error

warning: unused variable: `pos`
   --> src/main.rs:189:18
    |
189 |         for &(c, pos) in &a_grp {
    |                  ^^^ help: consider prefixing with an underscore: `_pos`
    |
    = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `i`
   --> src/main.rs:204:13
    |
204 |         for i in 0..append {
    |             ^ help: consider prefixing with an underscore: `_i`

Judge Result