Problem:
Score : 400 points

Problem Statement

There is a grid of square cells with H horizontal rows and W vertical columns. The cell at the i-th row and the j-th column will be denoted as Cell (i, j).

In Cell (i, j), a_{ij} coins are placed.

You can perform the following operation any number of times:

Operation: Choose a cell that was not chosen before and contains one or more coins, then move one of those coins to a vertically or horizontally adjacent cell.

Maximize the number of cells containing an even number of coins.

Constraints

All values in input are integers.

1 \leq H, W \leq 500

0 \leq a_{ij} \leq 9

Input

Input is given from Standard Input in the following format:

H W
a_{11} a_{12} ... a_{1W}
a_{21} a_{22} ... a_{2W}
:
a_{H1} a_{H2} ... a_{HW}

Output

Print a sequence of operations that maximizes the number of cells containing an even number of coins, in the following format:

N
y_1 x_1 y_1' x_1'
y_2 x_2 y_2' x_2'
:
y_N x_N y_N' x_N'

That is, in the first line, print an integer N between 0 and H \times W (inclusive), representing the number of operations.

In the (i+1)-th line (1 \leq i \leq N), print four integers y_i, x_i, y_i' and x_i' (1 \leq y_i, y_i' \leq H and 1 \leq x_i, x_i' \leq W), representing the i-th operation. These four integers represents the operation of moving one of the coins placed in Cell (y_i, x_i) to a vertically or horizontally adjacent cell, (y_i', x_i').

Note that if the specified operation violates the specification in the problem statement or the output format is invalid, it will result in Wrong Answer.

Sample Input 1

2 3
1 2 3
0 1 1

Sample Output 1

3
2 2 2 3
1 1 1 2
1 3 1 2

Every cell contains an even number of coins after the following sequence of operations:

Move the coin in Cell (2, 2) to Cell (2, 3).

Move the coin in Cell (1, 1) to Cell (1, 2).

Move one of the coins in Cell (1, 3) to Cell (1, 2).

Sample Input 2

3 2
1 0
2 1
1 0

Sample Output 2

3
1 1 1 2
1 2 2 2
3 1 3 2

Sample Input 3

1 5
9 9 9 9 9

Sample Output 3

2
1 1 1 2
1 3 1 4

Solution in Rust (1.15.1) (judge verdict: Accepted)

pub trait FromFragments: Sized {
    fn fragments_count() -> usize;
    fn from_fragments(fragments: &[&str]) -> Result<Self, String>;
}
impl FromFragments for String {
    fn fragments_count() -> usize {
        1
    }
    fn from_fragments(fragments: &[&str]) -> Result<String, String> {
        Ok(fragments[0].to_string())
    }
}
macro_rules ! impl_from_fragments { ( $ ( $ t : ty ) * ) => { $ ( impl FromFragments for $ t { fn fragments_count ( ) -> usize { 1 } fn from_fragments ( fragments : & [ & str ] ) -> Result <$ t , String > { use std :: str :: FromStr ; <$ t >:: from_str ( fragments [ 0 ] ) . map_err ( | _ | { format ! ( "cannot parse \"{}\" as {}" , fragments [ 0 ] , stringify ! ( $ t ) ) } ) } } ) * } ; }
impl_from_fragments ! ( isize usize i8 u8 i16 u16 i32 u32 i64 u64 f32 f64 ) ;
pub trait FromLine: Sized {
    fn from_line(line: &str) -> Result<Self, String>;
}
fn split_into_fragments(line: &str) -> Vec<&str> {
    line.trim_right_matches('\n').split_whitespace().collect()
}
impl<T: FromFragments> FromLine for T {
    fn from_line(line: &str) -> Result<T, String> {
        let fragments = split_into_fragments(line);
        if fragments.len() != T::fragments_count() {
            return Err(format!(
                "line \"{}\" has {} fragments, expected {}",
                line,
                fragments.len(),
                T::fragments_count()
            ));
        }
        T::from_fragments(&fragments)
    }
}
impl<T: FromFragments> FromLine for Vec<T> {
    fn from_line(line: &str) -> Result<Vec<T>, String> {
        let n = T::fragments_count();
        let fragments = split_into_fragments(line);
        if fragments.len() % n != 0 {
            return Err(format!(
                "line \"{}\" has {} fragments, expected multiple of {}",
                line,
                fragments.len(),
                n
            ));
        }
        let mut result = Vec::new();
        for chunk in fragments.chunks(n) {
            match T::from_fragments(chunk) {
                Ok(v) => result.push(v),
                Err(msg) => {
                    let flagment_msg = if n == 1 {
                        format!("fragment {}", result.len())
                    } else {
                        let l = result.len();
                        format!("fragments {}-{}", n * l + 1, (n + 1) * l)
                    };
                    return Err(format!("{} of line \"{}\": {}", flagment_msg, line, msg));
                }
            }
        }
        Ok(result)
    }
}
macro_rules ! impl_from_fragments_for_tuples { ( $ t : ident $ var : ident $ count : expr ) => ( ) ; ( $ t : ident $ var : ident $ count : expr ; $ ( $ inner_t : ident $ inner_var : ident $ inner_count : expr ) ;* ) => { impl_from_fragments_for_tuples ! ( $ ( $ inner_t $ inner_var $ inner_count ) ;* ) ; impl <$ t : FromFragments , $ ( $ inner_t : FromFragments ) ,*> FromFragments for ( $ t , $ ( $ inner_t ) ,* ) { fn fragments_count ( ) -> usize { let mut n = <$ t >:: fragments_count ( ) ; $ ( n += <$ inner_t >:: fragments_count ( ) ; ) * n } # [ allow ( unused_assignments ) ] fn from_fragments ( fragments : & [ & str ] ) -> Result < ( $ t , $ ( $ inner_t ) ,* ) , String > { let mut start = 0 ; let $ var = <$ t >:: from_fragments ( & fragments [ start .. start +<$ t >:: fragments_count ( ) ] ) ?; start += <$ t >:: fragments_count ( ) ; $ ( let $ inner_var = <$ inner_t >:: from_fragments ( & fragments [ start .. start +<$ inner_t >:: fragments_count ( ) ] ) ?; start += <$ inner_t >:: fragments_count ( ) ; ) * Ok ( ( $ var , $ ( $ inner_var ) ,* ) ) } } } }
impl_from_fragments_for_tuples ! ( T4 x4 4 ; T3 x3 3 ; T2 x2 2 ; T1 x1 1 ) ;
#[macro_export]
macro_rules ! read { ( ) => { let mut line = String :: new ( ) ; std :: io :: stdin ( ) . read_line ( & mut line ) . unwrap ( ) ; } ; ( $ pat : pat = $ t : ty ) => { let mut line = String :: new ( ) ; std :: io :: stdin ( ) . read_line ( & mut line ) . unwrap ( ) ; let $ pat = <$ t >:: from_line ( & line ) . unwrap ( ) ; } ; ( $ ( $ pat : pat = $ t : ty ) ,+ ) => { read ! ( ( $ ( $ pat ) ,* ) = ( $ ( $ t ) ,* ) ) ; } ; }
#[macro_export]
macro_rules ! readls { ( $ ( $ pat : pat = $ t : ty ) ,+ ) => { $ ( read ! ( $ pat = $ t ) ; ) * } }
pub fn read_vec<T: FromLine>() -> Vec<T> {
    use std::io::{self, BufRead};
    let stdin = io::stdin();
    let result = stdin
        .lock()
        .lines()
        .map(|line_result| {
            let line = line_result.expect("read from stdin failed");
            T::from_line(&line).unwrap()
        }).collect();
    result
}
#[macro_export]
macro_rules ! read_loop { ( $ pat : pat = $ t : ty ; $ block : block ) => { use std :: io :: BufRead ; let stdin = std :: io :: stdin ( ) ; for line in stdin . lock ( ) . lines ( ) { let line = line . expect ( "read from stdin failed" ) ; let $ pat = <$ t >:: from_line ( & line ) . unwrap ( ) ; $ block } } ; ( $ ( $ pat : pat = $ t : ty ) ,* ; $ block : block ) => { read_loop ! ( ( $ ( $ pat ) ,* ) = ( $ ( $ t ) ,* ) ; $ block ) ; } }
#[macro_export]
macro_rules ! readn_loop { ( $ n : expr ; $ pat : pat = $ t : ty ; $ block : block ) => { use std :: io :: BufRead ; let stdin = std :: io :: stdin ( ) ; { let lock = stdin . lock ( ) ; for _ in 0 ..$ n { let line = String :: new ( ) ; lock . read_line ( & mut line ) . expect ( "read from stdin failed" ) ; let $ pat = <$ t >:: from_line ( & line ) . unwrap ( ) ; $ block } } } ; ( $ n : expr ; $ ( $ pat : pat = $ t : ty ) ,* ; $ block : block ) => { read_times_loop ! ( $ n ; ( $ ( $ pat ) ,* ) = ( $ ( $ t ) ,* ) ; $ block ) ; } }

use std::fmt::{self, Display, Formatter};
use std::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct Vec2<T> {
    pub x: T,
    pub y: T,
}
impl<T> Vec2<T> {
    pub fn new(x: T, y: T) -> Vec2<T> {
        Vec2 { x: x, y: y }
    }
}
impl<T: Display> Display for Vec2<T> {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{} {}", self.x, self.y)
    }
}
impl<S, T: Add<S>> Add<Vec2<S>> for Vec2<T> {
    type Output = Vec2<T::Output>;
    fn add(self, rhs: Vec2<S>) -> Self::Output {
        Vec2::new(self.x + rhs.x, self.y + rhs.y)
    }
}
impl<S, T: AddAssign<S>> AddAssign<Vec2<S>> for Vec2<T> {
    fn add_assign(&mut self, rhs: Vec2<S>) {
        self.x += rhs.x;
        self.y += rhs.y;
    }
}
impl<S, T: Sub<S>> Sub<Vec2<S>> for Vec2<T> {
    type Output = Vec2<T::Output>;
    fn sub(self, rhs: Vec2<S>) -> Self::Output {
        Vec2::new(self.x - rhs.x, self.y - rhs.y)
    }
}
impl<S, T: SubAssign<S>> SubAssign<Vec2<S>> for Vec2<T> {
    fn sub_assign(&mut self, rhs: Vec2<S>) {
        self.x -= rhs.x;
        self.y -= rhs.y;
    }
}
impl<T: Neg> Neg for Vec2<T> {
    type Output = Vec2<T::Output>;
    fn neg(self) -> Self::Output {
        Vec2::new(-self.x, -self.y)
    }
}
macro_rules ! impl_mul_vec2 { ( $ ( $ t : ty ) * ) => { $ ( impl Mul < Vec2 <$ t >> for $ t { type Output = Vec2 <<$ t as Mul >:: Output >; fn mul ( self , rhs : Vec2 <$ t > ) -> Self :: Output { Vec2 :: new ( self * rhs . x , self * rhs . y ) } } ) * } }
impl_mul_vec2 ! ( i8 u8 i16 u16 i32 u32 i64 u64 f32 f64 ) ;
impl<S: Copy, T: Mul<S>> Mul<S> for Vec2<T> {
    type Output = Vec2<T::Output>;
    fn mul(self, rhs: S) -> Self::Output {
        Vec2::new(self.x * rhs, self.y * rhs)
    }
}
impl<S: Copy, T: MulAssign<S>> MulAssign<S> for Vec2<T> {
    fn mul_assign(&mut self, rhs: S) {
        self.x *= rhs;
        self.y *= rhs;
    }
}
impl<S: Copy, T: Div<S>> Div<S> for Vec2<T> {
    type Output = Vec2<T::Output>;
    fn div(self, rhs: S) -> Self::Output {
        Vec2::new(self.x / rhs, self.y / rhs)
    }
}
impl<S: Copy, T: DivAssign<S>> DivAssign<S> for Vec2<T> {
    fn div_assign(&mut self, rhs: S) {
        self.x /= rhs;
        self.y /= rhs;
    }
}
impl<T: FromFragments> FromFragments for Vec2<T> {
    fn fragments_count() -> usize {
        T::fragments_count() * 2
    }
    fn from_fragments(fragments: &[&str]) -> Result<Vec2<T>, String> {
        let n = T::fragments_count();
        Ok(Vec2::new(
            T::from_fragments(&fragments[..n])?,
            T::from_fragments(&fragments[n..])?,
        ))
    }
}

fn main() {
    read!(h = usize, w = usize);
    let board: Vec<Vec<u8>> = read_vec();

    let mut path: Vec<Vec2<usize>> = Vec::new();
    for y in 0..h {
        let range = 0..w;
        if y % 2 == 0 {
            for x in range {
                path.push(Vec2::new(x, y));
            }
        } else {
            for x in range.rev() {
                path.push(Vec2::new(x, y));
            }
        }
    }

    let mut indices = Vec::new();
    let mut is_holding = board[path[0].y][path[0].x] % 2 == 1;
    for i in 1..path.len() {
        let cur = path[i];
        if is_holding {
            indices.push(i);
            if board[cur.y][cur.x] % 2 == 1 {
                is_holding = false;
            }
        } else {
            if board[cur.y][cur.x] % 2 == 1 {
                is_holding = true;
            }
        }
    }

    println!("{}", indices.len());
    for i in indices {
        let p1 = path[i-1];
        let p2 = path[i];
        println!("{} {} {} {}", p1.y+1, p1.x+1, p2.y+1, p2.x+1);
    }
}