Problem:
Score : 200 points

Problem Statement

There is a grid of squares with H horizontal rows and W vertical columns.
The square at the i-th row from the top and the j-th column from the left is represented as (i, j).
Each square is black or white.
The color of the square is given as an H-by-W matrix (a_{i, j}).
If a_{i, j} is ., the square (i, j) is white; if a_{i, j} is #, the square (i, j) is black.

Snuke is compressing this grid.
He will do so by repeatedly performing the following operation while there is a row or column that consists only of white squares:

Operation: choose any one row or column that consists only of white squares, remove it and delete the space between the rows or columns.

It can be shown that the final state of the grid is uniquely determined regardless of what row or column is chosen in each operation.
Find the final state of the grid.

Constraints

1 \leq H, W \leq 100

a_{i, j} is . or #.

There is at least one black square in the whole grid.

Input

Input is given from Standard Input in the following format:

H W
a_{1, 1}...a_{1, W}
:
a_{H, 1}...a_{H, W}

Output

Print the final state of the grid in the same format as input (without the numbers of rows and columns); see the samples for clarity.

Sample Input 1

4 4
##.#
....
##.#
.#.#

Sample Output 1

###
###
.##

The second row and the third column in the original grid will be removed.

Sample Input 2

3 3
#..
.#.
..#

Sample Output 2

#..
.#.
..#

As there is no row or column that consists only of white squares, no operation will be performed.

Sample Input 3

4 5
.....
.....
..#..
.....

Sample Output 3

#

Sample Input 4

7 6
......
....#.
.#....
..#...
..#...
......
.#..#.

Sample Output 4

..#
#..
.#.
.#.
#.#

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

//using static System.Linq.Enumerable;
using static System.Console;
using static AtCoder.Util;
using static AtCoder.Cin;
using static System.Math;
using static AtCoder.MyMath;
using static AtCoder.StreamExtensions;

namespace AtCoder {
    static class Program {
        static void Main() {
            var h = ReadInt();
            var w = ReadInt();
            var a = ReadString(h).Select(x => x.ToList()).ToList();

            a.Call(Compress, 100).WriteMatrix();
        }

        static List<List<char>> Compress(List<List<char>> source) =>
            source.Where(x => x.Any(c => c == '#')).ToList().Transpose().Where(x => x.Any(c => c == '#')).ToList();
    }

}

/* ***************** Following Contents are my common library ******** */

namespace AtCoder {

    static class MyMath {
        public static long ToNearestInt(this double d) {
            var l = (long) Math.Floor(d);
            var r = l + 1;
            return r - d < d - l ? r : l;
        }

        public static long Factorial(this long n) => Range(1, n).Aggregate(1L, Multiply);
        public static long nPr(int n, int r) => r < 0 || r > n ? 0 : FromTo(n - r + 1, n).Select(x =>(long) x).Aggregate(1L, Multiply);
        public static long nCr(int n, int r) => nPr(n, r) / Factorial(r);

        public static long Inc(long i) => i + 1;
        public static long Dec(long i) => i - 1;
        public static long Plus(long i, long j) => i + j;
        public static Func<long, long> Plus(long j) => i => i + j;
        public static long Minus(long i, long j) => i - j;
        public static Func<long, long> Minus(long j) => i => i - j;
        public static long Multiply(long i, long j) => i * j;
        public static Func<long, long> Multiply(long j) => i => i * j;
        public static long Divide(long i, long j) => j / j;
        public static Func<long, long> Divide(long j) => i => i * j;
        public static long Mod(long i, long j) => i % j;
        public static Func<long, long> Mod(long j) => i => i % j;

        public static long Max(params long[] ns) => ns.Max();

        public static long LowerBound(this long m, long lbound) => Max(m, lbound);
        public static long UpperBound(this long m, long ubound) => Min(m, ubound);
        public static long Bound(this long m, long lowerBound, long UpperBound) => m.LowerBound(lowerBound).UpperBound(UpperBound);

        public static long LowerBound(this int m, long lbound) => Max(m, lbound);
        public static long UpperBound(this int m, long ubound) => Min(m, ubound);
        public static long Bound(this int m, long lowerBound, long UpperBound) => m.LowerBound(lowerBound).UpperBound(UpperBound);

        public static bool InRange(this long x, long min, long max) => min <= x && x <= max;
        public static bool IsEven(this int x) => x % 2 == 0;
        public static bool IsOdd(this int x) => x % 2 != 0;
        public static bool IsEven(this long x) => x % 2 == 0;
        public static bool IsOdd(this long x) => x % 2 != 0;

        public static IEnumerable<int> ToDigits(this long n) =>
            n.ToString().Select(x => x.ToInt());
        public static IEnumerable<int> ToDigits(this int n) =>((long) n).ToDigits();

        public static IEnumerable<int> Factors(this int n) {
            for (int i = 1; i <= n; i++)
                if (n % i == 0) yield return i;
        }

        public static IEnumerable<int> Natural() {
            for (int i = 0;; i++) yield return i;
        }
        public static IEnumerable<int> Positive() => Natural().Skip(1);

        public static long Pow(long i, long exp) =>(exp == 0) ? 1 : i * Pow(i, exp - 1);

    }

    static class Util {

        public static string Show(this IEnumerable<char> source) => new string(source.ToArray());
        public static HashSet<T> ToHashSet<T>(this IEnumerable<T> source) => new HashSet<T>(source);

        public static MultiSet<T> ToMultiSet<T>(this IEnumerable<T> t) => new MultiSet<T>(t);

        public static bool IsPalindrome(string s) {
            for (int i = 0; i < s.Length / 2; i++) {
                if (s[i] != s[s.Length - 1 - i]) return false;
            }
            return true;
        }
        public readonly static VectorInt2[] Dir8 = {
            new VectorInt2(-1, -1),
            new VectorInt2(-1, 0),
            new VectorInt2(-1, 1),
            new VectorInt2(0, -1),
            new VectorInt2(0, 1),
            new VectorInt2(1, -1),
            new VectorInt2(1, 0),
            new VectorInt2(1, 1)
        };

        public const long MODCONST = 1000000007;

        public static T debug<T>(this T value) {
            Console.Error.WriteLine($"debug:{value}");
            return value;
        }

        public static T Id<T>(T t) => t;
        public static long ToLong(this String s) => long.Parse(s);
        public static long ToLong(this char c) => c - '0';
        public static int ToInt(this String s) => int.Parse(s);
        public static int ToInt(this char c) => c - '0';

        public static VectorInt2 ReadVectorInt2() =>
            new VectorInt2(ReadInt(), ReadInt());

        public static string ReplaceX(this string input, string pattern, string replace) =>
            Regex.Replace(input, pattern, replace);

        public static IEnumerable<int> Range(int i, int j) => Enumerable.Range(i, j);
        public static IEnumerable<long> Range(long i, long j) {
            for (long k = i; k < i + j; k++) yield return k;

        }
        public static void Swap<T>(this IList<T> enumerable, int i, int j) {
            var buf = enumerable[i];
            enumerable[i] = enumerable[j];
            enumerable[j] = buf;

        }

        public static bool In<T>(this T t, IEnumerable<T> range) => range.Contains(t);

    }

    static class ParametricExtensions {
        public static Func<S, U> Then<S, T, U>(this Func<S, T> f, Func<T, U> g) => x => g(f(x));
        public static Func<S, U> Compose<S, T, U>(this Func<T, U> f, Func<S, T> g) => x => f(g(x));

        public static void Call<T>(this T t, Action<T> action) => action(t);
        public static void WriteLine<T>(this T t) => Console.WriteLine(t);
        public static T Call<S, T>(this S s, Func<S, T> func) => func(s);

        public static S Call<S>(this S s, Func<S, S> func, int times) => times == 0 ? s : Call(func(s), func, times - 1);

    }

    static class StreamExtensions {

        public static void ReverseRange<T>(this IList<T> enumerable, int i, int j) {
            int half = (j - i) / 2;
            for (int k = 0; k <= half; k++) enumerable.Swap(i + k, j - k);
        }

        public static bool isEmpty<T>(this IEnumerable<T> enumerable) => !enumerable.Any();
        public static void Times(this int n, Action action) {
            for (int i = 0; i < n; i++) action();
        }
        public static void Times(this long n, Action action) {
            for (long i = 0; i < n; i++) action();
        }

        public static IEnumerable<T> Times<T>(this int n, Func<T> func) {
            for (long i = 0; i < n; i++) yield return func();
        }
        public static IEnumerable<T> Times<T>(this long n, Func<T> func) {
            for (long i = 0; i < n; i++) yield return func();
        }

        public static void ForEach<T>(this IEnumerable<T> e, Action<T> action) {
            foreach (var v in e) action(v);
        }
        public static long Prod(this IEnumerable<long> source) => source.Aggregate(Multiply);

        public static IEnumerable<int> FromTo(int a, int b) => Range(a, Max(b - a + 1, 0));
        public static IEnumerable<T> Repeat<T>(T t) {
            while (true) yield return t;
        }
        public static IEnumerable<T> Replicate<T>(int n, T t) => Repeat(t).Take(n);

        public static IEnumerable<T> Cycle<T>(this IEnumerable<T> e) {
            while (true)
                foreach (var v in e) yield return v;
        }

        public static IEnumerable<T> Scan<S, T>(this IEnumerable<S> source, T init, Func<T, S, T> accumulator) {
            var result = init;
            foreach (var item in source) {
                result = accumulator(result, item);
                yield return result;
            }
        }

        public static T[] ToArray<T>(params T[] ns) => ns;
        public static List<T> ToList<T>(params T[] ns) => ns.ToList();

        public static IEnumerable<T> Scan0<S, T>(this IEnumerable<S> source, T init, Func<T, S, T> accumulator) {
            yield return init;
            foreach (var item in Scan(source, init, accumulator)) yield return item;
        }

        public static IEnumerable<Tuple<T1, T2>> Cartesian<T1, T2>(IEnumerable<T1> s1, IEnumerable<T2> s2) =>
            from v1 in s1 from v2 in s2 select new Tuple<T1, T2>(v1, v2);

        public static IEnumerable<Tuple<T1, T2, T3>> Cartesian<T1, T2, T3>(IEnumerable<T1> s1, IEnumerable<T2> s2, IEnumerable<T3> s3) =>
            from v1 in s1 from v2 in s2 from v3 in s3 select new Tuple<T1, T2, T3>(v1, v2, v3);

        public static IEnumerable<Tuple<T1, T2, T3, T4>> Cartesian<T1, T2, T3, T4>(IEnumerable<T1> s1, IEnumerable<T2> s2, IEnumerable<T3> s3, IEnumerable<T4> s4) =>
            from v1 in s1 from v2 in s2 from v3 in s3 from v4 in s4 select new Tuple<T1, T2, T3, T4>(v1, v2, v3, v4);

        public static IEnumerable<List<T>> Buffer<T>(this IEnumerable<T> source, int length) {
            while (source.Any()) {
                yield return source.Take(length).ToList();
                source = source.Skip(length);
            }
        }

        public static T MaxBy<T>(this IEnumerable<T> source, Func<T, long> selector) {
            T max = source.First();
            foreach (var item in source)
                if (selector(item) > selector(max)) max = item;
            return max;
        }

        public static T MinBy<T>(this IEnumerable<T> source, Func<T, long> selector) {
            T min = source.First();
            foreach (var item in source)
                if (selector(item) < selector(min)) min = item;
            return min;
        }

        public static int IndexOf<T>(this IList<T> source, Func<T, bool> condition) {
            for (int i = 0; i < source.Count; i++)
                if (condition(source[i]))
                    return i;

            return -1;
        }
        public static IEnumerable<List<T>> ChunkBy<T>(this IEnumerable<T> source) => ChunkBy(source, Id, EqualityComparer<T>.Default);
        public static IEnumerable<List<T>> ChunkBy<S, T>(this IEnumerable<T> source, Func<T, S> selector) => ChunkBy(source, selector, EqualityComparer<S>.Default);
        public static IEnumerable<List<T>> ChunkBy<S, T>(this IEnumerable<T> source, Func<T, S> selector, IEqualityComparer<S> comparer) {
            while (source.Any()) {
                var v = selector(source.First());
                var l = source.TakeWhile(x => comparer.Equals(selector(x), v)).ToList();
                yield return l;
                source = source.Skip(l.Count());
            }
        }
    }

    static class Matrix {
        public static List<List<T>> Transpose<T>(this List<List<T>> source) =>
            Range(0, source[0].Count).Select(i => source.Select(x => x[i]).ToList()).ToList();

        public static void WriteMatrix(this IEnumerable<IEnumerable<char>> source) {
            foreach (var line in source) {
                line.Show().WriteLine();
            }
        }
    }

    static class Cin {
        private static Queue<string> tokens;
        static Cin() {
            string line;
            tokens = new Queue<string>();
            while ((line = Console.ReadLine()) != null) {
                foreach (var token in line.Split(' ')) {
                    tokens.Enqueue(token);
                }
            }
        }

        static public int ReadInt() => int.Parse(tokens.Dequeue());
        static public List<int> ReadInt(long n) {
            var list = new List<int>();
            n.Times(() => list.Add(ReadInt()));
            return list;
        }
        static public long ReadLong() => long.Parse(tokens.Dequeue());
        static public List<long> ReadLong(long n) {
            var list = new List<long>();
            n.Times(() => list.Add(ReadLong()));
            return list;
        }
        static public string ReadString() => tokens.Dequeue();
        static public List<string> ReadString(long n) {
            var list = new List<string>();
            n.Times(() => list.Add(ReadString()));
            return list;
        }

        static public void SayYesNo(this bool b) =>(b ? "Yes" : "No").WriteLine();
    }

    struct VectorInt2 {
        public int X { get; set; }
        public int Y { get; set; }

        public VectorInt2(int x, int y) {
            X = x;
            Y = y;
        }

        static public VectorInt2 operator +(VectorInt2 v1, VectorInt2 v2) =>
            new VectorInt2(v1.X + v2.X, v1.Y + v2.Y);
        static public VectorInt2 operator -(VectorInt2 v1, VectorInt2 v2) =>
            new VectorInt2(v1.X - v2.X, v1.Y - v2.Y);
        static public VectorInt2 operator *(VectorInt2 v1, VectorInt2 v2) =>
            new VectorInt2(v1.X * v2.X, v1.Y * v2.Y);
        static public VectorInt2 operator *(VectorInt2 v1, int i) =>
            new VectorInt2(v1.X * i, v1.Y * i);
        static public VectorInt2 operator *(int i, VectorInt2 v2) =>
            new VectorInt2(i * v2.X, i * v2.Y);
        static public VectorInt2 operator /(VectorInt2 v1, int i) =>
            new VectorInt2(v1.X / i, v1.Y / i);

        public override string ToString() => $"({X}, {Y})";
    }

    class MultiSet<T> : IEnumerable<KeyValuePair<T, int>> {
        Dictionary<T, int> dictionary = new Dictionary<T, int>();

        public MultiSet(IEnumerable<T> data) {
            foreach (var datum in data) {
                if (dictionary.ContainsKey(datum)) {
                    dictionary[datum]++;
                } else {
                    dictionary[datum] = 1;
                }
            }
        }

        public bool Contains(T t) => dictionary.ContainsKey(t);

        public void RemoveIfAny(T t) {
            if (dictionary.ContainsKey(t)) {
                dictionary[t]--;
                if (dictionary[t] == 0) {
                    dictionary.Remove(t);
                }
            }
        }

        public int this [T key] {
            get {
                return dictionary.ContainsKey(key) ? dictionary[key] : 0;
            }
        }
        public MultiSet() {}

        public static MultiSet<S> ToMultiSet<S>(IEnumerable<S> source) => new MultiSet<S>(source);

        public Dictionary<T, int> AsDict() => dictionary;

        public IEnumerator<KeyValuePair<T, int>> GetEnumerator() => dictionary.GetEnumerator();
        IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
    }
}