Problem:
Score : 300 points

Problem Statement

There is a grid with H rows and W columns, where each square is painted black or white.

You are given H strings S_1, S_2, ..., S_H, each of length W.
If the square at the i-th row from the top and the j-th column from the left is painted black, the j-th character in the string S_i is #; if that square is painted white, the j-th character in the string S_i is ..

Find the number of pairs of a black square c_1 and a white square c_2 that satisfy the following condition:

There is a path from the square c_1 to the square c_2 where we repeatedly move to a vertically or horizontally adjacent square through an alternating sequence of black and white squares: black, white, black, white...

Constraints

1 \leq H, W \leq 400

|S_i| = W (1 \leq i \leq H)

For each i (1 \leq i \leq H), the string S_i consists of characters # and ..

Input

Input is given from Standard Input in the following format:

H W
S_1
S_2
:
S_H

Output

Print the answer.

Sample Input 1

3 3
.#.
..#
#..

Sample Output 1

10

Some of the pairs satisfying the condition are ((1, 2), (3, 3)) and ((3, 1), (3, 2)), where (i, j) denotes the square at the i-th row from the top and the j-th column from the left.

Sample Input 2

2 4
....
....

Sample Output 2

0

Sample Input 3

4 3
###
###
...
###

Sample Output 3

6

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

#[allow(unused_imports)]
use std::cmp::{min,max};
#[allow(unused_imports)]
use std::collections::{BTreeMap,BTreeSet};
#[allow(unused_imports)]
use std::ops::*;
#[allow(unused_imports)]
use std::collections::BinaryHeap;

#[allow(unused_macros)]
macro_rules! ite {
    ($c:expr, $t:expr, $f:expr) => {{
        if $c { $t } else { $f }
    }};
}

// ref: tanakh <https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8>
// diff: using Parser
#[macro_export]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut parser = Parser::from_str($s);
        input_inner!{parser, $($r)*}
    };
    (parser = $parser:ident, $($r:tt)*) => {
        input_inner!{$parser, $($r)*}
    };
    (new_stdin_parser = $parser:ident, $($r:tt)*) => {
        let stdin = std::io::stdin();
        let reader = std::io::BufReader::new(stdin.lock());
        let mut $parser = Parser::new(reader);
        input_inner!{$parser, $($r)*}
    };
    ($($r:tt)*) => {
        input!{new_stdin_parser = parser, $($r)*}
    };
}

#[macro_export]
macro_rules! input_inner {
    ($parser:ident) => {};
    ($parser:ident, ) => {};
    ($parser:ident, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($parser, $t);
        input_inner!{$parser $($r)*}
    };
}

#[macro_export]
macro_rules! read_value {
    ($parser:ident, ( $($t:tt),* )) => {
        ( $(read_value!($parser, $t)),* )
    };
    ($parser:ident, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($parser, $t)).collect::<Vec<_>>()
    };
    ($parser:ident, chars) => {
        read_value!($parser, String).chars().collect::<Vec<char>>()
    };
    ($parser:ident, usize1) => {
        read_value!($parser, usize) - 1
    };
    ($parser:ident, $t:ty) => {
        $parser.next::<$t>().expect("Parse error")
    };
}

fn main() {
    input! {
        h: usize,
        w: usize,
        field: [chars; h],
    }
    let mut uf = UnionFind::new(h*w);
    let dx = [0, 1, 0, -1];
    let dy = [1, 0, -1, 0];
    for y in 0..h {
        for x in 0..w {
            for d in 0..4 {
                let nx = x as i64 + dx[d];
                let ny = y as i64 + dy[d];
                if 0 <= nx && nx < w as i64 && 0 <= ny && ny < h as i64 {
                    if field[y][x] != field[ny as usize][nx as usize] {
                        uf.unite(y*w+x, ny as usize * w + nx as usize);
                    }
                }
            }
        }
    }
    let mut b_count = vec![vec![0i64; w]; h];
    let mut w_count = vec![vec![0i64; w]; h];
    for y in 0..h {
        for x in 0..w {
            let r = uf.root(y*w+x);
            let ry = r / w;
            let rx = r % w;
            if field[y][x] == '#' {
                b_count[ry][rx] += 1;
            }
            else {
                w_count[ry][rx] += 1;
            }
        }
    }
    let mut res = 0i64;
    for y in 0..h {
        for x in 0..w {
            res += b_count[y][x] * w_count[y][x];
        }
    }
    println!("{}", res);
}

use std::io::BufRead;
use std::io;
use std::str;

// ref: tatsuya6502 <https://qiita.com/tatsuya6502/items/cd448486f7ef7b5b8c7e>
// ref: wariuni <https://qiita.com/tatsuya6502/items/cd448486f7ef7b5b8c7e#comment-7040a5ae96305e884eb9>
// diff: using std::io::BufRead::fill_buf()
pub struct Parser<R> {
    reader: R,
    buf: Vec<u8>,
    pos: usize,
}

impl Parser<io::Empty> {
    pub fn from_str(s: &str) -> Parser<io::Empty> {
        Parser {
            reader: io::empty(),
            buf: s.as_bytes().to_vec(),
            pos: 0,
        }
    }
}

impl<R:BufRead> Parser<R> {
    pub fn new(reader: R) -> Parser<R> {
        Parser {
            reader: reader,
            buf: vec![],
            pos: 0,
        }
    }
    pub fn update_buf(&mut self) {
        self.buf.clear();
        self.pos = 0;
        loop {
            let (len,complete) = {
                let buf2 = self.reader.fill_buf().unwrap();
                self.buf.extend_from_slice(buf2);
                let len = buf2.len();
                (len, buf2[len-1] <= 0x20)
            };
            self.reader.consume(len);
            if complete {
                break;
            }
        }
    }
    pub fn next<T:str::FromStr>(&mut self) -> Result<T, T::Err> {
        loop {
            let mut begin = self.pos;
            while begin < self.buf.len() && (self.buf[begin] <= 0x20) {
                begin += 1;
            }
            let mut end = begin;
            while end < self.buf.len() && (self.buf[end] > 0x20) {
                end += 1;
            }
            if begin != self.buf.len() {
                self.pos = end;
                return str::from_utf8(&self.buf[begin..end]).unwrap().parse::<T>();
            }
            else {
                self.update_buf();
            }
        }
    }
}

struct UnionFindNode {
    parent: usize,
    num: usize,
}

impl UnionFindNode {
    fn new(parent: usize) -> UnionFindNode {
        UnionFindNode {
            parent: parent,
            num: 1,
        }
    }
}

pub struct UnionFind(Vec<UnionFindNode>);

impl UnionFind {
    pub fn new(n: usize) -> UnionFind {
        let mut xs = vec![];
        for i in 0..n {
            xs.push(UnionFindNode::new(i));
        }
        UnionFind(xs)
    }
    pub fn root(&mut self, i: usize) -> usize {
        let parent = self.0[i].parent;
        if parent == i {
            i
        }
        else {
            let res = self.root(parent);
            self.0[i].parent = res;
            res
        }
    }
    pub fn unite(&mut self, i: usize, k: usize) {
        let i = self.root(i);
        let k = self.root(k);
        if i == k {
            return;
        }
        let (i,k) = if self.0[i].num < self.0[k].num {
            (i,k)
        }
        else {
            (k,i)
        };
        self.0[i].parent = k;
        self.0[k].num += self.0[i].num;
    }
    pub fn is_same_set(&mut self, i: usize, k: usize) -> bool {
        self.root(i) == self.root(k)
    }
    pub fn num(&mut self, i: usize) -> usize {
        let i = self.root(i);
        self.0[i].num
    }
}

struct Writer {
    s: String,
}

use std::fmt::Display;
impl Writer {
    pub fn new() -> Writer {
        Writer {
            s: String::new(),
        }
    }
    pub fn flush(&mut self) {
        print!("{}", self.s);
        self.s.clear();
    }
    pub fn write<T: Display>(&mut self, x: T) {
        self.s.push_str(&format!("{}", x));
    }
    pub fn writeln<T: Display>(&mut self, x: T) {
        self.s.push_str(&format!("{}", x));
        self.s.push('\n');
    }
    #[allow(dead_code)]
    pub fn write_vec<T: Display>(&mut self, xs: &Vec<T>) {
        if xs.len() == 0 {
            self.writeln("");
            return;
        }
        self.write(&format!("{}", xs[0]));
        for i in 1..xs.len() {
            self.write(&format!(" {}", xs[i]));
        }
        self.writeln("");
    }
}