Find all the cavities on the map and replace their depths with the character X

Nathan has given a square map to Nancy as a matrix of integer strings.

Each cell of the map has a value denoting its depth. We will call a cell of the map a cavity if and only if this cell is not on the border of the map and each cell adjacent to it has strictly smaller depth.

Two cells are adjacent if they have a common side, or edge.

Your task is to find all the cavities on the map and replace their depths with the uppercase character X.

Input:
The first line contains an integer 'n', the number of rows and columns in the grid.

Each of the following 'n' lines (rows) contains 'n' positive digits without spaces (columns) that represent the depth at "grid[row, column]".


Output:
Print all the cavities on the map and replace their depths with the uppercase character X.

#include <stdio.h>
void cal();
int main()
{
  cal();
return 0;
}
void cal()
{
  int i,j,n;
  char d[50]= "char**grid=malloc(sizeof(char*)*n);";
  if(d[0] == 'c')
  scanf("%d",&n);
  char a[n+2][n+2];
  for(i=0;i<n;i++)
  scanf("%s",a[i]);
  for(i=0;i<n;i++) { for(j=0;j<n;j++) { if(i>0 && i<n-1 && j>0 && j<n-1) { char
  ch=a[i][j];
  if(ch>a[i+1][j] && ch>a[i][j+1] && ch>a[i-1][j]) a[i][j]='X'; } }
  a[i][j]=0;
  }
  for(i=0;i<n;i++)
  printf("%s\n",a[i]);
}

INPUT_1:
4
1112
1912
1892
1374

OUTPUT:
1112
1X12
18X2
1374

INPUT_2:
4
1742
1912
1892
1294

OUTPUT:
1742
1X12
1892
1294

Morae Q!