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Find safe cells in a matrix

  • Difficulty Level : Basic
  • Last Updated : 15 Jun, 2021
Geek Week

Given a matrix mat[][] containing the characters Z, P and * where Z is a zombie, P is a plant and * is a bare land. Given that a zombie can attack a plant if the plant is adjacent to the zombie (total 8 adjacent cells are possible). The task is to print the number of plants that are safe from the zombies.

Examples: 

Input: 
mat[] = { "**P*",
          "*Z**", 
          "*Z**", 
          "***P" }
Output: 1

Input: 
mat[] = { "**P*P", 
          "*Z**", 
          "*P**", 
          "***P" }
Output: 2

Approach: Traverse the matrix element by element, if the current element is a plant i.e. mat[i][j] = ‘P’ then check if the plant is surrounded by any zombie (in all the 8 adjacent cells). If the plant is safe then update count = count + 1. Print the count in the end.

Below is the implementation of the above approach: 

C++




// C++ implementation of the approach
#include <iostream>
using namespace std;
 
// Function that returns true if mat[i][j] is a zombie
bool isZombie(int i, int j, int r, int c, string mat[])
{
    if (i < 0 || j < 0 || i >= r || j >= c
        || mat[i][j] != 'Z')
        return false;
 
    return true;
}
 
// Function to return the count of plants
// that survived from the zombies attack
int Plant_Vs_Zombies(string mat[], int row, int col)
{
    int i, j, count = 0;
 
    for (i = 0; i < row; i++) {
        for (j = 0; j < col; j++) {
 
            // If current cell is a plant
            if (mat[i][j] == 'P') {
 
                // If current plant is safe from zombies
                if (!isZombie(i - 1, j - 1, row, col, mat)
                    && !isZombie(i - 1, j, row, col, mat)
                    && !isZombie(i - 1, j + 1, row, col, mat)
                    && !isZombie(i, j - 1, row, col, mat)
                    && !isZombie(i, j, row, col, mat)
                    && !isZombie(i, j + 1, row, col, mat)
                    && !isZombie(i + 1, j - 1, row, col, mat)
                    && !isZombie(i + 1, j, row, col, mat)
                    && !isZombie(i + 1, j + 1, row, col, mat)) {
                    count++;
                }
            }
        }
    }
 
    return count;
}
 
// Driver Code
int main()
{
    // Input matrix
    string mat[] = { "**P*", "*Z**", "*Z**", "***P" };
 
    // Rows and columns of the matrix
    int row = sizeof(mat) / sizeof(mat[0]);
    int col = mat[0].length();
 
    // Total plants survived
    cout << Plant_Vs_Zombies(mat, row, col);
}

Java




// Java implementation of the approach.
 
class GfG
{
 
    // Function that returns true if
    // mat[i][j] is a zombie
    static boolean isZombie(int i, int j, int r,
                            int c, String mat[])
    {
        if (i < 0 || j < 0 || i >= r || j >= c
            || mat[i].charAt(j) != 'Z')
            return false;
     
        return true;
    }
     
    // Function to return the count of plants
    // that survived from the zombies attack
    static int Plant_Vs_Zombies(String mat[],
                            int row, int col)
    {
        int i, j, count = 0;
     
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
     
                // If current cell is a plant
                if (mat[i].charAt(j) == 'P')
                {
     
                    // If current plant is safe from zombies
                    if (!isZombie(i - 1, j - 1, row, col, mat)
                        && !isZombie(i - 1, j, row, col, mat)
                        && !isZombie(i - 1, j + 1, row, col, mat)
                        && !isZombie(i, j - 1, row, col, mat)
                        && !isZombie(i, j, row, col, mat)
                        && !isZombie(i, j + 1, row, col, mat)
                        && !isZombie(i + 1, j - 1, row, col, mat)
                        && !isZombie(i + 1, j, row, col, mat)
                        && !isZombie(i + 1, j + 1, row, col, mat)) {
                        count++;
                    }
                }
            }
        }
        return count;
    }
 
    // Driver code
    public static void main(String []args)
    {
         
        // Input matrix
        String[] mat = { "**P*", "*Z**", "*Z**", "***P" };
     
        // Rows and columns of the matrix
        int row = mat.length;
        int col = mat[0].length();
     
        // Total plants survived
        System.out.println(Plant_Vs_Zombies(mat, row, col));
    }
}
 
// This code is contributed by Rituraj Jain

Python3




# Python3 implementation of the approach.
 
# Function that returns true if
# mat[i][j] is a zombie
def isZombie(i, j, r, c, mat):
 
    if (i < 0 or j < 0 or i >= r or
        j >= c or mat[i][j] != 'Z'):
        return True;
 
    return False;
 
# Function to return the count of plants
# that survived from the zombies attack
def Plant_Vs_Zombies(mat, row, col):
 
    count = 0;
 
    for i in range(row):
        for j in range(col):
 
            # If current cell is a plant
            if (mat[i][j] == 'P'):
 
                # If current plant is safe from zombies
                if (isZombie(i - 1, j - 1, row, col, mat) and
                    isZombie(i - 1, j, row, col, mat) and
                    isZombie(i - 1, j + 1, row, col, mat) and
                    isZombie(i, j - 1, row, col, mat) and
                    isZombie(i, j, row, col, mat) and
                    isZombie(i, j + 1, row, col, mat) and
                    isZombie(i + 1, j - 1, row, col, mat) and
                    isZombie(i + 1, j, row, col, mat) and
                    isZombie(i + 1, j + 1, row, col, mat)):
                    count += 1;
    return count;
 
# Driver code
 
# Input matrix
mat = ["**P*", "*Z**", "*Z**", "***P"];
 
# Rows and columns of the matrix
row = len(mat);
col = len(mat[0]);
 
# Total plants survived
print(Plant_Vs_Zombies(mat, row, col));
 
# This code is contributed by mits

C#




// C# implementation of the approach.
using System;
 
class GfG
{
 
    // Function that returns true if
    // mat[i][j] is a zombie
    static bool isZombie(int i, int j, int r,
                            int c, String []mat)
    {
        if (i < 0 || j < 0 || i >= r || j >= c
            || mat[i][j] != 'Z')
            return false;
     
        return true;
    }
     
    // Function to return the count of plants
    // that survived from the zombies attack
    static int Plant_Vs_Zombies(String []mat,
                            int row, int col)
    {
        int i, j, count = 0;
     
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
     
                // If current cell is a plant
                if (mat[i][j] == 'P')
                {
     
                    // If current plant is safe from zombies
                    if (!isZombie(i - 1, j - 1, row, col, mat)
                        && !isZombie(i - 1, j, row, col, mat)
                        && !isZombie(i - 1, j + 1, row, col, mat)
                        && !isZombie(i, j - 1, row, col, mat)
                        && !isZombie(i, j, row, col, mat)
                        && !isZombie(i, j + 1, row, col, mat)
                        && !isZombie(i + 1, j - 1, row, col, mat)
                        && !isZombie(i + 1, j, row, col, mat)
                        && !isZombie(i + 1, j + 1, row, col, mat))
                    {
                        count++;
                    }
                }
            }
        }
        return count;
    }
 
    // Driver code
    public static void Main(String []args)
    {
         
        // Input matrix
        String[] mat = { "**P*", "*Z**", "*Z**", "***P" };
     
        // Rows and columns of the matrix
        int row = mat.Length;
        int col = mat[0].Length;
     
        // Total plants survived
        Console.WriteLine(Plant_Vs_Zombies(mat, row, col));
    }
}
 
// This code contributed by Rajput-Ji

PHP




<?php
// PHP implementation of the approach.
 
// Function that returns true if
// mat[i][j] is a zombie
function isZombie($i, $j, $r, $c, $mat)
{
    if ($i < 0 || $j < 0 || $i >= $r ||
        $j >= $c || $mat[$i][$j] != 'Z')
        return false;
 
    return true;
}
 
// Function to return the count of plants
// that survived from the zombies attack
function Plant_Vs_Zombies($mat, $row, $col)
{
    $i; $j; $count = 0;
 
    for ($i = 0; $i < $row; $i++)
    {
        for ($j = 0; $j < $col; $j++)
        {
 
            // If current cell is a plant
            if ($mat[$i][$j] == 'P')
            {
 
                // If current plant is safe from zombies
                if (!isZombie($i - 1, $j - 1, $row, $col, $mat) &&
                    !isZombie($i - 1, $j, $row, $col, $mat) &&
                    !isZombie($i - 1, $j + 1, $row, $col, $mat) &&
                    !isZombie($i, $j - 1, $row, $col, $mat) &&
                    !isZombie($i, $j, $row, $col, $mat) &&
                    !isZombie($i, $j + 1, $row, $col, $mat) &&
                    !isZombie($i + 1, $j - 1, $row, $col, $mat) &&
                    !isZombie($i + 1, $j, $row, $col, $mat) &&
                    !isZombie($i + 1, $j + 1, $row, $col, $mat))
                {
                    $count++;
                }
            }
        }
    }
    return $count;
}
 
// Driver code
 
// Input matrix
$mat = array( "**P*", "*Z**", "*Z**", "***P" );
 
// Rows and columns of the matrix
$row = sizeof($mat);
$col = strlen($mat[0]);
 
// Total plants survived
echo(Plant_Vs_Zombies($mat, $row, $col));
 
// This code is contributed by Code_Mech.
?>

Javascript




<script>
 
// Javascript implementation of the approach.
 
// Function that returns true if
// mat[i][j] is a zombie
function isZombie(i, j, r, c, mat)
{
    if (i < 0 || j < 0 || i >= r ||
       j >= c || mat[i][j] != 'Z')
        return false;
   
    return true;
}
   
// Function to return the count of plants
// that survived from the zombies attack
function Plant_Vs_Zombies(mat, row, col)
{
    let i, j, count = 0;
   
    for(i = 0; i < row; i++)
    {
        for(j = 0; j < col; j++)
        {
             
            // If current cell is a plant
            if (mat[i][j] == 'P')
            {
                 
                // If current plant is safe from zombies
                if (!isZombie(i - 1, j - 1, row, col, mat) &&
                    !isZombie(i - 1, j, row, col, mat) &&
                    !isZombie(i - 1, j + 1, row, col, mat) &&
                    !isZombie(i, j - 1, row, col, mat) &&
                    !isZombie(i, j, row, col, mat) &&
                    !isZombie(i, j + 1, row, col, mat) &&
                    !isZombie(i + 1, j - 1, row, col, mat) &&
                    !isZombie(i + 1, j, row, col, mat) &&
                    !isZombie(i + 1, j + 1, row, col, mat))
                {
                    count++;
                }
            }
        }
    }
    return count;
}
 
// Driver code
 
// Input matrix
let mat = [ "**P*", "*Z**", "*Z**", "***P" ];
 
// Rows and columns of the matrix
let row = mat.length;
let col = mat[0].length;
 
// Total plants survived
document.write(Plant_Vs_Zombies(mat, row, col));
 
// This code is contributed by mukesh07
 
</script>
Output: 
1

 

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