C#练习题答案: 简单有趣＃85：多边形周边【难度：2级】--景越C#经典编程题库,1000道C#基础练习题等你来挑战

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这篇博客提供了10种不同的解决方案来解答一道C#编程练习，涉及多边形周边的处理，难度为二级。每种答案都详细阐述了不同方法，适合C#初学者和进阶者提升技能。

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简单有趣#85:多边形周边【难度:2级】:

答案1:

namespace myjinxin
{
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix){
          
            int numSides = 0;
            
            for (int row = 0; row < matrix.Length; row++)
            {
                for (int col = 0; col < matrix[row].Length; col++)
                {
                    
                    if (matrix[row][col])  // if the square is true, check if matrix edge, or neighbor is false
                    {
                        numSides += ( col == 0                    || !matrix[row][col-1] ) ? 1 : 0 ;   // left
                        numSides += ( col == matrix[row].Length-1 || !matrix[row][col+1] ) ? 1 : 0 ;   // right
                        numSides += ( row == 0                    || !matrix[row-1][col] ) ? 1 : 0 ;   // top
                        numSides += ( row == matrix.Length-1      || !matrix[row+1][col] ) ? 1 : 0 ;   // bottom
                    }
                    
                }
            }
            return numSides;
        }
    }
}

答案2:

namespace myjinxin
{
    using System;

    public class Kata
    {
        public bool IsEdge(bool[][] array, int y, int x)
        {
            try
            {
                return (array[y][x] == false) ? true : false; //if it is false, it is an edge. Otherwise, it is "true" and not an edge.
            }
            catch (IndexOutOfRangeException)
            {
                return true; //if it is out of range, it is an edge
            }
        }
        public int PolygonPerimeter(bool[][] matrix)
        {
            var edges = 0;
            for (var y = 0; y < matrix.Length; y++) //iterate through each array in array
            {
                for (var x = 0; x < matrix[y].Length; x++) ///iterate through elements in each array
                {
                    if (matrix[y][x]) 
                    {
                        if (IsEdge(matrix, y, x + 1)) edges++; //checks to see if neighboring positions are edges relative to matrix[y][x]
                        if (IsEdge(matrix, y, x - 1)) edges++; 
                        if (IsEdge(matrix, y + 1, x)) edges++; 
                        if (IsEdge(matrix, y - 1, x)) edges++;
                    }
                }
            }
            return edges;
        }
    }
}

答案3:

namespace myjinxin
{
    using System;
    using System.Linq;
    
    public class Kata
    {
    public  int PolygonPerimeter(bool[][] matrix)
    {
        int per = 0;
        for (int i = 0; i < matrix.Count(); i++) {
            for(int j = 0; j < matrix[i].Count(); j++){
                if (matrix[i][j] == true) {
                    per+=(i > 0) ? (matrix[i - 1][j] ? 0 : 2):2;
                    per+=(j > 0) ? (matrix[i][j - 1] ? 0 : 2):2;
                }
            }
        }
        return per;
    }
    }
}

答案4:

namespace myjinxin {
    public class Kata {

        private bool IsBlackCell( bool[][] matrix, int rowIndex, int columnIndex ) {
            if ( rowIndex < 0 || rowIndex >= matrix.Length ) {
                return false;
            }
            var row = matrix[ rowIndex ];
            if ( columnIndex < 0 || columnIndex >= row.Length ) {
                return false;
            }
            return matrix[ rowIndex ][ columnIndex ];
        }

        public int PolygonPerimeter( bool[][] matrix ) {
            var perimeter = 0;
            for ( int i = 0; i < matrix.Length; i++ ) {
                var row = matrix[ i ];
                for ( int j = 0; j < row.Length; j++ ) {
                    if ( !IsBlackCell( matrix, i, j ) ) {
                        continue;
                    }
                    if ( !IsBlackCell( matrix, i - 1, j ) ) {
                        perimeter += 1;
                    }
                    if ( !IsBlackCell( matrix, i + 1, j ) ) {
                        perimeter += 1;
                    }
                    if ( !IsBlackCell( matrix, i, j - 1 ) ) {
                        perimeter += 1;
                    }
                    if ( !IsBlackCell( matrix, i, j + 1 ) ) {
                        perimeter += 1;
                    }
                }
            }
            return perimeter;
        }

    }
}

答案5:

using System;

namespace myjinxin
{
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix){
          //coding and coding..
          int perimeter = 0;
          for(int i = 0; i < matrix.Length; i++) {
            for(int j = 0; j < matrix[0].Length; j++){
                if(matrix[i][j]){
                    if(i+1 < matrix.Length &amp;&amp; !matrix[i+1][j]) perimeter++;
                    if(i-1 >= 0 &amp;&amp; !matrix[i-1][j]) perimeter++;
                    if(j+1 < matrix[0].Length &amp;&amp; !matrix[i][j+1]) perimeter++;
                    if(j-1 >= 0 &amp;&amp; !matrix[i][j-1]) perimeter++;
                    
                    
                    if(i+1 == matrix.Length) perimeter++;
                    if(i-1 < 0) perimeter++;
                    if(j+1 == matrix[0].Length) perimeter++;
                    if(j-1 < 0) perimeter++;

                }
            }
          }
          
          return perimeter;
        }
        
    }
}

答案6:

namespace myjinxin
{
    using System;    
  public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix)
        {
            int res = 0;
            for (int i = 0; i < matrix.Length; i++)
            {
                for (int j = 0; j < matrix[0].Length; j++)
                {
                    if(i != matrix.Length - 1) if (matrix[i][j] &amp;&amp; matrix[i + 1][j]) res--;
                    if(i != 0) if (matrix[i][j] &amp;&amp; matrix[i - 1][j]) res--;
                    if (matrix[i][j] == true) res += 4;
                }
            }
            for (int j = 0; j < matrix.Length; j++)
            {
                for (int i = 0; i < matrix[0].Length - 1; i++) if (matrix[j][i] &amp;&amp; matrix[j][i + 1]) res -= 2;
            }
            return res;
        }
        }
}

答案7:

namespace myjinxin
{
    using System;
    
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix){
          var sum = 0;
          for(int i=0; i< matrix.Length; i++){
            for(int j=0; j< matrix[i].Length; j++){
              if(matrix[i][j]){
                sum += 4;
                sum -= NumberOfBlackNeighbours(matrix, i, j);
              }
            }
          }
          return sum;
        }
        
        private int NumberOfBlackNeighbours(bool[][] matrix, int x, int y){
          var res = 0;
          //horizontal
          if(y < matrix[x].Length - 1 &amp;&amp; matrix[x][y+1])
            res ++;
          if(y > 0 &amp;&amp; matrix[x][y-1])
            res ++;
          //vertical
          if(x < matrix.Length - 1 &amp;&amp; matrix[x+1][y])
            res ++;
          if(x > 0 &amp;&amp; matrix[x-1][y])
            res ++;
          return res;
        }
    }
}

答案8:

namespace myjinxin
{
    using System;
    
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix)
        {
            var perimeter = 0;

            for (var rowIdx = 0; rowIdx < matrix.Length; rowIdx++)
            {
                var reachedTop = rowIdx == 0;
                var reachedBottom = rowIdx == matrix.Length - 1;

                for (var columnIdx = 0; columnIdx < matrix[rowIdx].Length; columnIdx++)
                {
                    var reachedLeft = columnIdx == 0;
                    var reachedRight = columnIdx == matrix[rowIdx].Length - 1;
                    var isFilled = matrix[rowIdx][columnIdx];

                    if (isFilled)
                    {
                        if (reachedTop || !matrix[rowIdx - 1][columnIdx])
                            perimeter++;

                        if (reachedBottom || !matrix[rowIdx + 1][columnIdx])
                            perimeter++;

                        if (reachedRight || !matrix[rowIdx][columnIdx + 1])
                            perimeter++;

                        if (reachedLeft || !matrix[rowIdx][columnIdx - 1])
                            perimeter++;
                    }
                }
            }

            return perimeter;


        }
    }
}

答案9:

namespace myjinxin
{
    using System;
    
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix)
        {
            int perimeter = 0;
            var rowCount = matrix.Length;
            var colCount = matrix[0].Length;
            for (int i = 0; i < rowCount; i++)
            {
                for (int j = 0; j < colCount; j++)
                {
                    // -- Black cell --
                    if (matrix[i][j])
                    {
                        // ----- Check LEFT -----
                        if (j == 0)
                        {
                            perimeter++;
                        }
                        // -> Cell to the LEFT is white <-
                        else if (!matrix[i][j - 1])
                        {
                            perimeter++;
                        }
                        // ----- Check RIGHT -----
                        if (j == colCount - 1)
                        {
                            perimeter++;
                        }
                        // -> Cell to the RIGHT is white <-
                        else if (!matrix[i][j + 1])
                        {
                            perimeter++;
                        }
                        // ----- Check UP -----
                        if (i == 0)
                        {
                            perimeter++;
                        }
                        // -> Cell ABOVE is white <-
                        else if (!matrix[i - 1][j])
                        {
                            perimeter++;
                        }
                        // ----- Check DOWN -----
                        if (i == rowCount - 1 )
                        {
                            perimeter++;
                        }
                        // -> Cell BELOW is white <-
                        else if (!matrix[i + 1][j])
                        {
                            perimeter++;
                        }
                    }
                }
            }
            
            return perimeter;
        }
    }
}

答案10:

namespace myjinxin
{
    using System;
    
    public class Kata
    {
        public int PolygonPerimeter(bool[][] matrix)
        {
          int polygons = 0;
          
          for(int x = 0; x < matrix.Length; x++)
          {
            for(int y = 0; y < matrix[0].Length; y++)
            {
              Console.WriteLine("h");
              if(matrix[x][y] == true)
              {
                Console.WriteLine("l");
                for(int i = -1; i <= 1; i++)
                {
                  for(int n = -1; n <= 1; n++)
                  {
                    if((i == 0 &amp;&amp; n == 0) || (i == -1 &amp;&amp; n == -1) || (i == -1 &amp;&amp; n == 1) || (i == 1 &amp;&amp; n == -1) || (i == 1 &amp;&amp; n == 1))
                      continue;
                    if(x+i < 0 || x+i > matrix.Length-1)
                      polygons++;
                    else if(y+n < 0 || y+n > matrix[0].Length-1)
                      polygons++;
                    else if(matrix[x+i][y+n] == false)
                      polygons++;
                  }
                }
              }
            }
          }
          Console.WriteLine("-----------------");
          return polygons;
        }
    }
}