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Count the number of survivors
• Difficulty Level : Medium
• Last Updated : 16 Oct, 2019

Given a matrix mat[][] containing the characters [1 – 9], P and * where P is a person and * is an empty space. An integer in the current cell denotes a bomb that can destroy object within the radius equal to the value of the cell. The task is to count and print the number of persons that will survive the blast.

Examples:

```Input:
mat[] = { "P***",
"****",
"2**P",
"****" }
Output: 1
Only the person in the third row
will survive. Note that the person
in the first row is within the

Input:
mat[] = { "2***P*",
"P*****",
"******",
"**1***",
"******",
"*****P" }
Output: 2
The persons in the first and last
row survive.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: Traverse the matrix character by character, if the current character is a digit (1 – 9) then change all the surrounding elements within the radius to * (in all eight directions) indicating that no one survived within that radius. After all the elements of the matrix have been traversed, count the number of cell indicating a person i.e. mat[i][j] = ‘P’. Print the count in the end.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach``#include ``using` `namespace` `std;`` ` `// Function to return the count of``// the people that survived``int` `countSurvivors(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 bomb``            ``if` `(mat[i][j] > ``'0'` `&& mat[i][j] <= ``'9'``) {``                ``int` `radius = mat[i][j] - ``'0'``;`` ` `                ``// Coordinates of the sub-matrix``                ``// that will be affected by the blast``                ``int` `iMin = max(i - radius, 0);``                ``int` `iMax = min(i + radius, row - 1);``                ``int` `jMin = max(j - radius, 0);``                ``int` `jMax = min(j + radius, col - 1);`` ` `                ``for` `(``int` `k = iMin; k <= iMax; k++)``                    ``for` `(``int` `l = jMin; l <= jMax; l++)`` ` `                        ``// Set the current cell to``                        ``//  empty space without a person``                        ``mat[k][l] = ``'*'``;``            ``}``        ``}``    ``}`` ` `    ``// Count the remaining persons``    ``for` `(i = 0; i < row; i++)``        ``for` `(j = 0; j < col; j++)``            ``if` `(mat[i][j] == ``'P'``)``                ``count++;`` ` `    ``return` `count;``}`` ` `// Driver Code``int` `main()``{``    ``// Input matrix``    ``string mat[] = { ``"P***"``, ``"****"``, ``"2**P"``, ``"****"` `};`` ` `    ``// Rows and columns of the matrix``    ``int` `row = ``sizeof``(mat) / ``sizeof``(mat);``    ``int` `col = mat.length();`` ` `    ``// Total people survived``    ``cout << countSurvivors(mat, row, col);``}`

## Java

 `// Java implementation of the approach ``class` `GFG``{`` ` `// Function to return the count of ``// the people that survived ``static` `int` `countSurvivors(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 bomb ``                ``if` `(mat[i].charAt(j) > ``'0'` `&& mat[i].charAt(j) <= ``'9'``) ``                ``{ ``                    ``int` `radius = mat[i].charAt(j) - ``'0'``; ``     ` `                    ``// Coordinates of the sub-matrix ``                    ``// that will be affected by the blast ``                    ``int` `iMin = Math.max(i - radius, ``0``); ``                    ``int` `iMax = Math.min(i + radius, row - ``1``); ``                    ``int` `jMin = Math.max(j - radius, ``0``); ``                    ``int` `jMax = Math.min(j + radius, col - ``1``); ``     ` `                    ``for` `(``int` `k = iMin; k <= iMax; k++) ``                    ``{``                         ` `                        ``// convert string nto character array``                        ``char` `C [] = mat[k].toCharArray();``                         ` `                        ``for` `(``int` `l = jMin; l <= jMax; l++) ``                        ``{``                            ``// Set the current cell to ``                            ``// empty space without a person ``                            ``C [l] = ``'*'` `; ``                        ``}``                        ``// convert character array back into the string``                        ``String s = ``new` `String(C) ;``                        ``mat[k] = s ;``                    ``}``                ``} ``            ``} ``        ``} ``     ` `        ``// Count the remaining persons ``        ``for` `(i = ``0``; i < row; i++) ``            ``for` `(j = ``0``; j < col; j++) ``                ``if` `(mat[i].charAt(j) == ``'P'``) ``                    ``count++; ``     ` `        ``return` `count; ``    ``} ``     ` `    ``// Driver Code ``    ``public` `static` `void` `main(String []args)``    ``{ ``        ``// Input matrix ``        ``String mat[] = { ``"P***"``, ``"****"``, ``"2**P"``, ``"****"` `}; ``     ` `        ``// Rows and columns of the matrix ``        ``int` `row = mat.length ; ``        ``int` `col = mat[``0``].length(); ``     ` `        ``// Total people survived ``        ``System.out.println(countSurvivors(mat, row, col)); ``    ``} ``}`` ` `// This code is contributed by Ryuga`

## Python3

 `# Python3 implementation of the approach``import` `math as mt`` ` `# Function to return the count of``# the people that survived``def` `countSurvivors(mat, row, col):`` ` `    ``i, j, count ``=` `0``, ``0``, ``0`` ` `    ``for` `i ``in` `range``(row): ``        ``for` `j ``in` `range``(col): `` ` `            ``# If current cell is a bomb``            ``if` `(mat[i][j] > ``'0'` `and` `mat[i][j] <``=` `'9'``): ``                ``radius ``=` `ord``(mat[i][j]) ``-` `ord``(``'0'``)`` ` `                ``# Coordinates of the sub-matrix``                ``# that will be affected by the blast``                ``iMin ``=` `max``(i ``-` `radius, ``0``)``                ``iMax ``=` `min``(i ``+` `radius, row ``-` `1``)``                ``jMin ``=` `max``(j ``-` `radius, ``0``)``                ``jMax ``=` `min``(j ``+` `radius, col ``-` `1``)`` ` `                ``for` `k ``in` `range``(iMin, iMax ``+` `1``):``                    ``for` `l ``in` `range``(jMin, jMax ``+` `1``):`` ` `                        ``# Set the current cell to``                        ``# empty space without a person``                        ``mat[k][l] ``=` `'*'``             ` `    ``# Count the remaining persons``    ``for` `i ``in` `range``(row):``        ``for` `j ``in` `range``(col):``            ``if` `(mat[i][j] ``=``=` `'P'``):``                ``count ``+``=` `1`` ` `    ``return` `count`` ` `# Driver Code`` ` `# Input matrix``mat ``=` `[[``"P"``, ``"*"``, ``"*"``, ``"*"``], ``       ``[``"*"``, ``"*"``, ``"*"``, ``"*"``], ``       ``[``"2"``, ``"*"``, ``"*"``, ``"P"``],``       ``[``"*"``, ``"*"``, ``"*"``, ``"*"``]]`` ` `# Rows and columns of the matrix``row ``=` `len``(mat)``col ``=` `len``(mat[``0``])`` ` `# Total people survived``print``(countSurvivors(mat, row, col))`` ` `# This code is contributed by``# Mohit Kumar 29`

## C#

 `// C# implementation of the approach``using` `System;``using` `System.Collections.Generic;``     ` `class` `GFG``{`` ` `// Function to return the count of ``// the people that survived ``static` `int` `countSurvivors(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 bomb ``            ``if` `(mat[i][j] > ``'0'` `&& mat[i][j] <= ``'9'``) ``            ``{ ``                ``int` `radius = mat[i][j] - ``'0'``; `` ` `                ``// Coordinates of the sub-matrix ``                ``// that will be affected by the blast ``                ``int` `iMin = Math.Max(i - radius, 0); ``                ``int` `iMax = Math.Min(i + radius, row - 1); ``                ``int` `jMin = Math.Max(j - radius, 0); ``                ``int` `jMax = Math.Min(j + radius, col - 1); `` ` `                ``for` `(``int` `k = iMin; k <= iMax; k++) ``                ``{``                     ` `                    ``// convert string nto character array``                    ``char` `[]C = mat[k].ToCharArray();``                     ` `                    ``for` `(``int` `l = jMin; l <= jMax; l++) ``                    ``{``                        ``// Set the current cell to ``                        ``// empty space without a person ``                        ``C [l] = ``'*'``; ``                    ``}``                    ``// convert character array back into the string``                    ``String s = ``new` `String(C);``                    ``mat[k] = s;``                ``}``            ``} ``        ``} ``    ``} `` ` `    ``// Count the remaining persons ``    ``for` `(i = 0; i < row; i++) ``        ``for` `(j = 0; j < col; j++) ``            ``if` `(mat[i][j] == ``'P'``) ``                ``count++; `` ` `    ``return` `count; ``} `` ` `// Driver Code ``public` `static` `void` `Main(String []args)``{ ``    ``// Input matrix ``    ``String []mat = { ``"P***"``, ``"****"``, ``                     ``"2**P"``, ``"****"` `}; `` ` `    ``// Rows and columns of the matrix ``    ``int` `row = mat.Length ; ``    ``int` `col = mat.Length; `` ` `    ``// Total people survived ``    ``Console.WriteLine(countSurvivors(mat, row, col)); ``} ``}`` ` `// This code is contributed by Rajput-Ji`
Output:
```1
```

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