#![allow(unused_imports)]
use std::io::*;
use std::fmt::*;
use std::str::*;
use std::cmp::*;
use std::collections::*;

pub trait InputValue {
    fn parse(s: &str) -> Self;
}

pub fn read<T: InputValue>() -> T {
    let mut buf = String::new();
    let _ = stdin().read_line(&mut buf);
    T::parse(&buf.trim())
}

pub fn readn<T: InputValue>(n: usize) -> Vec<T> {
    let mut vec = vec![];
    for _ in 0..n {
        vec.push(read());
    }
    vec
}

pub fn readnc<T: InputValue>() -> Vec<T> {
    let mut vec = vec![];
    let line: String = read();
    for token in line.split_whitespace() {
        vec.push(T::parse(token));
    }
    vec
}

macro_rules! parse_single_value {
    ($($t:ty),*) => {
        $(
            impl InputValue for $t {
                fn parse(s: &str) -> $t { s.parse().unwrap() }
            }
        )*
	}
}
parse_single_value!(i32, i64, f32, f64, usize, String);

macro_rules! parse_tuple {
	($($t:ident),*) => {
		impl<$($t),*> InputValue for ($($t),*) where $($t: InputValue),* {
			fn parse(s: &str) -> ($($t),*) {
				let mut tokens = s.split_whitespace();
				let t = ($($t::parse(tokens.next().unwrap())),*);
				t
			}
		}
	}
}
parse_tuple!(A, B);

// ===

struct UnionFind {
    parent: Vec<usize>,
    count: Vec<usize>
}

impl UnionFind {
    fn new(n: usize) -> Self {
        let mut parent = vec![];
        let mut count = vec![];
        for i in 0..n {
            parent.push(i);
            count.push(1);
        }
        UnionFind { parent: parent, count: count }
    }

    fn unite(&mut self, u: usize, v: usize) {
        let pu = self.find(u);
        let pv = self.find(v);
        if pu == pv {
            return;
        }
        self.parent[pu] = self.parent[pv];
        self.parent[pv] = self.parent[pu];

        let to = self.count[pu] + self.count[pv];
        self.count[pu] = to;
        self.count[pv] = to;
    }

    fn find(&mut self, u: usize) -> usize {
        let p = self.parent[u];
        if p == u {
            return p;
        }
        let root = self.find(p);
        self.parent[u] = root;
        let rc = self.count[root];
        self.count[u] = rc;
        return root;
    }
}

fn main() {
    let (h, w): (usize, usize) = read();
    let mut table: Vec<Vec<u8>> = vec![];
    for i in 0..h {
        let s: String = read();
        table.push(s.into_bytes());
    }
    let mut uf = UnionFind::new(h*w);


    let dx = [-1, 0, 1, 0];
    let dy = [0, 1, 0, -1];
    for i in 1..h+1 {
        for j in 1..w+1 {
            for d in 0..4 {
                let ti = (i as i32 + dy[d]) as usize;
                let tj = (j as i32 + dx[d]) as usize;
                if ti <= 0 || tj <= 0 || ti > h || tj > w {
                    continue
                }
                if table[i-1][j-1] == b'#' && table[ti-1][tj-1] == b'#' {
                    uf.unite((i-1)*w+j-1, (ti-1)*w+tj-1);
                }
            }
        }
    }

    let mut isok = true;
    for i in 0..h {
        for j in 0..w {
            if table[i][j] == b'#' && uf.count[i*w+j] == 1 {
                isok = false;
            }
        }
    }
    if isok {
        println!("Yes");
    } else {
        println!("No");
    }
}


Measured memory_bytes: 4352