在矩阵中查找具有最多星星的矩阵中的字母

给定一个由*和小写英文字母组成的矩阵垫，任务是找到周围带有最大*的字符(也包括对角线元素)。如果两个字符的最大计数相同，则按字典顺序打印最小的字符。
资料来源：邵逸夫面试经历
例子：

Input: 
mat[][] = {{'b', '*', '*', '*'}, 
           {'*', '*', 'c', '*'}, 
           {'*', 'a', '*', '*'}, 
           {'*', '*', '*', 'd'}}
Output: a
'a', 'b', 'c' and 'd' are surrounded by 
'7', '3', '7' and '3' stars respectively.
'a' and 'c' are surrounded by maximum stars 
but 'a' is lexicographically smaller than 'c'.

Input: 
mat[][] = {{'*', 'r', '*', '*'}, 
           {'m', 'a', 'z', '*'}, 
           {'l', '*', 'f', 'k'}, 
           {'*', '*', '*', 'd'} }
Output: f

方法：想法是遍历矩阵，如果找到一个字符，则计算它周围的星星数。检查它周围的所有8个位置，并计算起动次数。
使用地图跟踪字符和周围的星星数量。然后遍历地图，找到被最大星星包围且在字典上最小的字符。
下面是上述方法的实现：

C++

// C++ program to find alphabet in a Matrix
// which has maximum number of stars
// surrounding it
#include 
using namespace std;
 
// Function to return the count of stars
// around a particular index
int countStars(int mat[][4], int i, int j, int n)
{
    int count = 0;
 
    int rowNum[] = { -1, -1, -1, 0, 0, 1, 1, 1 };
    int colNum[] = { -1, 0, 1, -1, 1, -1, 0, 1 };
 
    // consider all 8 neighbours
    for (int k = 0; k < 8; k++) {
        int x = i + rowNum[k];
        int y = j + colNum[k];
        if (x >= 0 && x < n && y >= 0 && y < n
            && mat[x][y] == '*')
            count++;
    }
 
    return count;
}
 
// Function to return the character in a Matrix
// which has maximum number of stars around it
char alphabetWithMaxStars(int mat[][4], int n)
{
    unordered_map umap;
 
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
 
            // If current element is a character
            if ((mat[i][j] - 97) >= 0
                && (mat[i][j] - 97) < 26) {
                // Count of start surrounding it
                int stars = countStars(mat, i, j, n);
                umap[mat[i][j]] = stars;
            }
        }
    }
 
    int max = -1;
    char result = 'z' + 1;
 
    // Traverse the map
    for (auto x : umap) {
        if (x.second > max || (x.second == max
                               && x.first < result)) {
            max = x.second;
            result = x.first;
        }
    }
 
    return result;
}
 
// Driver code
int main()
{
    int mat[][4] = { { 'b', '*', '*', '*' },
                     { '*', '*', 'c', '*' },
                     { '*', 'a', '*', '*' },
                     { '*', '*', '*', 'd' } };
 
    int n = 4;
 
    cout << alphabetWithMaxStars(mat, n);
 
    return 0;
}

Java

// Java program to find alphabet in a Matrix
// which has maximum number of stars
// surrounding it
import java.util.*;
 
class GFG
{
 
// Function to return the count of stars
// around a particular index
static int countStars(int mat[][], int i, int j, int n)
{
    int count = 0;
 
    int rowNum[] = { -1, -1, -1, 0, 0, 1, 1, 1 };
    int colNum[] = { -1, 0, 1, -1, 1, -1, 0, 1 };
 
    // consider all 8 neighbours
    for (int k = 0; k < 8; k++)
    {
        int x = i + rowNum[k];
        int y = j + colNum[k];
        if (x >= 0 && x < n && y >= 0 && y < n
            && mat[x][y] == '*')
            count++;
    }
 
    return count;
}
 
// Function to return the character in a Matrix
// which has maximum number of stars around it
static char alphabetWithMaxStars(int mat[][], int n)
{
    HashMap umap =
        new HashMap();
 
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
 
            // If current element is a character
            if ((mat[i][j] - 97) >= 0
                && (mat[i][j] - 97) < 26)
            {
                 
                // Count of start surrounding it
                int stars = countStars(mat, i, j, n);
                umap.put((char)mat[i][j], stars);
            }
        }
    }
 
    int max = -1;
    char result = 'z' + 1;
 
    // Traverse the map
    for (Map.Entry x : umap.entrySet())
    {
        if (x.getValue() > max || (x.getValue() == max
            && x.getKey() < result))
        {
            max = x.getValue();
            result = x.getKey();
        }
    }
 
    return result;
}
 
// Driver code
public static void main(String[] args)
{
    int mat[][] = { { 'b', '*', '*', '*' },
                    { '*', '*', 'c', '*' },
                    { '*', 'a', '*', '*' },
                    { '*', '*', '*', 'd' } };
 
    int n = 4;
 
    System.out.print(alphabetWithMaxStars(mat, n));
}
}
 
// This code is contributed by PrinciRaj1992

Python3

# Python3 program to find alphabet in a
# Matrix which has maximum number of stars
# surrounding it
import math as mt
 
# Function to return the count of stars
# around a particular index
def countStars(mat, i, j, n):
 
    count = 0
 
    rowNum = [-1, -1, -1, 0, 0, 1, 1, 1 ]
    colNum = [-1, 0, 1, -1, 1, -1, 0, 1 ]
 
    # consider all 8 neighbours
    for k in range(8):
        x = i + rowNum[k]
        y = j + colNum[k]
        if (x >= 0 and x < n and y >= 0 and
            y < n and mat[x][y] == '*'):
            count += 1
     
    return count
 
# Function to return the character in a Matrix
# which has maximum number of stars around it
def alphabetWithMaxStars(mat, n):
 
    umap = dict()
 
    for i in range(n):
        for j in range(n):
 
            # If current element is a character
            if ((ord(mat[i][j]) - 97) >= 0 and
                (ord(mat[i][j]) - 97) < 26):
                # Count of start surrounding it
                stars = countStars(mat, i, j, n)
                umap[mat[i][j]] = stars
             
    Max = -1
    result = chr(ord('z') + 1)
 
    # Traverse the map
    for x in umap:
        if (umap[x] > Max or
           (umap[x] == Max and x < result)):
            Max = umap[x]
            result = x
         
    return result
 
# Driver code
mat = [[ 'b', '*', '*', '*' ],
       [ '*', '*', 'c', '*' ],
       [ '*', 'a', '*', '*' ],
       [ '*', '*', '*', 'd' ]]
 
n = 4
 
print(alphabetWithMaxStars(mat, n))
 
# This code is contributed by
# Mohit kumar 29

C#

// C# program to find alphabet in a Matrix
// which has maximum number of stars
// surrounding it
using System;
using System.Collections.Generic;
 
class GFG
{
 
// Function to return the count of stars
// around a particular index
static int countStars(int [,]mat, int i, int j, int n)
{
    int count = 0;
 
    int []rowNum = { -1, -1, -1, 0, 0, 1, 1, 1 };
    int []colNum = { -1, 0, 1, -1, 1, -1, 0, 1 };
 
    // consider all 8 neighbours
    for (int k = 0; k < 8; k++)
    {
        int x = i + rowNum[k];
        int y = j + colNum[k];
        if (x >= 0 && x < n && y >= 0 && y < n
            && mat[x, y] == '*')
            count++;
    }
 
    return count;
}
 
// Function to return the character in a Matrix
// which has maximum number of stars around it
static char alphabetWithMaxStars(int [,]mat, int n)
{
    Dictionary umap =
        new Dictionary();
 
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
 
            // If current element is a character
            if ((mat[i, j] - 97) >= 0
                && (mat[i, j] - 97) < 26)
            {
                 
                // Count of start surrounding it
                int stars = countStars(mat, i, j, n);
                if(umap.ContainsKey((char)mat[i,j]))
                    umap[(char)mat[i,j]] = stars;
                else
                    umap.Add((char)mat[i,j], stars);
            }
        }
    }
 
    int max = -1;
    char result = (char)('z' + 1);
 
    // Traverse the map
    foreach(KeyValuePair x in umap)
    {
        if (x.Value > max || (x.Value == max
            && x.Key < result))
        {
            max = x.Value;
            result = x.Key;
        }
    }
 
    return result;
}
 
// Driver code
public static void Main(String[] args)
{
    int [,]mat = { { 'b', '*', '*', '*' },
                    { '*', '*', 'c', '*' },
                    { '*', 'a', '*', '*' },
                    { '*', '*', '*', 'd' } };
 
    int n = 4;
 
    Console.Write(alphabetWithMaxStars(mat, n));
}
}
 
// This code is contributed by Rajput-Ji

输出：

a

另一种方法：

C++

// C++ program to find alphabet in a Matrix
// which has maximum number of stars
// surrounding it
#include 
using namespace std;
 
/**
    * Counts the number of stars around the letter at position i,j
    * start at position max(i-1,0),max(j-1,0) and iterate the 3*3 mini matrix
    * while watching out the boundaries of
    * our main matrix. 
    * @param i
    * @param j
    * @param mat
    * @return
    */
int countStars(int i, int j, vector> mat)
{
    int initialRow = i != 0 ? i - 1 : i;
    int initialCol = j != 0 ? j - 1 : j;
    int stars = 0;
    for (int row=initialRow;(row <= i + 1) &&
         row < mat.size() ; row++)
    {
        for (int col=initialCol;(col <= j + 1) &&
             col < mat.size() ; col++)
        {
            if (mat[row][col] == '*')
            {
                stars++;
            }
        }
    }
    return stars;
}
 
// Function to return the character in a Matrix
// which has maximum number of stars around it
char getStarredLetter (vector> mat)
{
    char currentSuperStar = 'a';
    int currentFans = 0;
    for (int i = 0 ; i < mat.size() ; i++)
    {
        vector row = mat[i];
        for (int j = 0 ; j < row.size(); j++)
        {
            char currentChar = row[j];
            if (currentChar != '*')
            {
                // Count of start surrounding it
                int fans = countStars(i, j, mat);
                if (fans > currentFans)
                {
                    currentSuperStar = currentChar;
                    currentFans = fans;
                }
                else if(fans == currentFans &&
                        currentChar < currentSuperStar)
                {
                    currentSuperStar = currentChar;
                }
            }
        }
    }
    return currentSuperStar;
}
 
// Driver Code
int main()
{
    vector> mat = { { 'b', '*', '*', '*' },
                                { '*', '*', 'c', '*' },
                                { '*', 'a', '*', '*' },
                                { '*', '*', '*', 'd' } };
    cout << getStarredLetter(mat);
    return 0;
}
 
// This code is contributed by rag2127.

Java

// Java program to find alphabet in a Matrix
// which has maximum number of stars
// surrounding it
public class SuperStarLetter {
     
    // Function to return the character in a Matrix
    // which has maximum number of stars around it
    private static char getStarredLetter (char[][] mat) {
        char currentSuperStar = 'a';
        int currentFans = 0;
        for (int i=0 ; i < mat.length ; i++) {
            char[] row = mat[i];
            for (int j = 0 ; j < row.length; j++) {
                char currentChar = row[j];
                if (currentChar != '*') {
                     
                    // Count of start surrounding it
                    int fans = countStars(i, j, mat);
                    if (fans > currentFans) {
                        currentSuperStar = currentChar;
                        currentFans = fans;
                    } else if (fans == currentFans &&
                            currentChar < currentSuperStar) {
                        currentSuperStar = currentChar;
                    }
                }
            }
        }
        return currentSuperStar;
    }
 
    /**
    * Counts the number of stars around the letter at position i,j
    * start at position max(i-1,0),max(j-1,0) and iterate the 3*3 mini matrix
    * while watching out the boundaries of
    * our main matrix.
    * @param i
    * @param j
    * @param mat
    * @return
    */
    private static int countStars(int i, int j, char[][] mat) {
        int initialRow = i != 0 ? i-1 : i;
        int initialCol = j != 0 ? j-1 : j;
        int stars= 0;
        for (int row=initialRow;(row <= i+1) && row < mat.length ; row++) {
            for (int col=initialCol;(col <= j+1) && col < mat.length ; col++) {
                if (mat[row][col] == '*') {
                    stars++;
                }
            }
        }
        return stars;
    }
        //Driver Code
    public static void main(String[] args) {
        char[][] mat = { { 'b', '*', '*', '*' },
                     { '*', '*', 'c', '*' },
                     { '*', 'a', '*', '*' },
                     { '*', '*', '*', 'd' } };
        System.out.println(getStarredLetter(mat));
         
    }
 
}

Python3

# Python3 program to find alphabet
# in a Matrix which has maximum
# number of stars surrounding it
 
# Function to return the character
# in a Matrix which has maximum
# number of stars around it
def getStarredLetter (mat) :
    currentSuperStar = 'a'
    currentFans = 0
    for i in range(len(mat)) :
        row = mat[i]
         
        for j in range(len(row)) :
             
            currentChar = row[j]
            if (currentChar != '*') :
                     
                # Count of start surrounding it
                fans = countStars(i, j, mat)
                if (fans > currentFans) :
                    currentSuperStar = currentChar
                    currentFans = fans
                 
                elif (fans == currentFans and
                      currentChar < currentSuperStar) :
                    currentSuperStar = currentChar;
                     
    return currentSuperStar;
     
"""
    * Counts the number of stars around the
    * letter at position i,j start at position
    * max(i-1,0),max(j-1,0) and iterate the 3*3
    * mini matrix while watching out the boundaries
    * of our main matrix.
    * @param i
    * @param j
    * @param mat
    * @return
"""
def countStars(i, j, mat) :
     
    if i != 0 :
        initialRow = i - 1
    else :
        initialRow = i
         
     
    if j != 0 :
        initialCol = j - 1
    else :
        initialCol = j
         
    stars = 0
     
    row = initialRow
     
    while ((row <= i + 1) and (row < len(mat))):
        col = initialCol
        while ((col <= j + 1) and (col < len(mat))):
            if (mat[row][col] == '*') :
                 
                stars += 1
             
            col += 1
             
        row += 1
         
    return stars
     
# Driver Code
if __name__ == "__main__" :
     
    mat = [ [ 'b', '*', '*', '*' ],
            [ '*', '*', 'c', '*' ],
            [ '*', 'a', '*', '*' ],
            [ '*', '*', '*', 'd' ] ]
             
    print(getStarredLetter(mat))
         
# This code is contributed by Ryugaa

C＃

// C# program to find row with
// max sum in a matrix
using System;
 
public class SuperStarLetter
{
     
    // Function to return the character in a Matrix
    // which has maximum number of stars around it
    private static char getStarredLetter (char[,] mat)
    {
        char currentSuperStar = 'a';
        int currentFans = 0;
        for (int i = 0 ; i < mat.GetLength(0) ; i++)
        {
            char[] row = GetRow(mat, i);
            for (int j = 0 ; j < row.Length; j++)
            {
                char currentChar = row[j];
                if (currentChar != '*')
                {
                     
                    // Count of start surrounding it
                    int fans = countStars(i, j, mat);
                    if (fans > currentFans)
                    {
                        currentSuperStar = currentChar;
                        currentFans = fans;
                    }
                    else if (fans == currentFans &&
                            currentChar < currentSuperStar)
                    {
                        currentSuperStar = currentChar;
                    }
                }
            }
        }
        return currentSuperStar;
    }
     
public static char[] GetRow(char[,] matrix, int row)
{
    var rowLength = matrix.GetLength(1);
    var rowVector = new char[rowLength];
 
    for (var i = 0; i < rowLength; i++)
    rowVector[i] = matrix[row, i];
 
    return rowVector;
}
    /**
    * Counts the number of stars around the letter at position i,j
    * start at position max(i-1,0),max(j-1,0) and iterate the 3*3 mini matrix
    * while watching out the boundaries of
    * our main matrix.
    * @param i
    * @param j
    * @param mat
    * @return
    */
    private static int countStars(int i, int j, char[,] mat)
    {
        int initialRow = i != 0 ? i-1 : i;
        int initialCol = j != 0 ? j-1 : j;
        int stars= 0;
        for (int row = initialRow;(row <= i+1) && row < mat.GetLength(0) ; row++)
        {
            for (int col=initialCol;(col <= j+1) && col < mat.GetLength(1); col++)
            {
                if (mat[row,col] == '*')
                {
                    stars++;
                }
            }
        }
        return stars;
    }
     
    // Driver Code
    public static void Main(String[] args)
    {
        char[,] mat = { { 'b', '*', '*', '*' },
                    { '*', '*', 'c', '*' },
                    { '*', 'a', '*', '*' },
                    { '*', '*', '*', 'd' } };
        Console.WriteLine(getStarredLetter(mat));
         
    }
}
 
// This code has been contributed by 29AjayKumar

输出：

a