BSQ — Biggest Square

Find and mark the largest square without obstacles in a rectangular map. This is a classic algorithmic project (in C) from the Epitech curriculum.

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🎯 Goal

Write a program bsq that reads a map (from a file or standard input), locates the largest possible square of empty cells, fills it with a dedicated character, and then prints the modified map to standard output.

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🧾 Input format

There are two common variants of the subject. Your evaluator will specify which one is required. The project must support the chosen variant and properly handle errors.

42 variant (legend on the first line)

• Line 1: N<empty><obstacle><full> where:

  • N = number of lines in the map (positive integer)
  • <empty> = character for empty cells
  • <obstacle> = character for obstacles
  • <full> = character used to fill the biggest square

• Lines 2..N+1: N lines of equal length composed only of <empty> and <obstacle>.

Example

9.ox
...........................
....o......................
......................o....
...............o...........
...........................
.................o.........
.......o...................
...........................
....o......................

Epitech variant (implicit legend)

• Line 1: N (number of lines)
• Lines 2..N+1: . for empty, o for obstacle, and the program must display the square filled with x.

Example

9
...........................
....o......................
......................o....
...............o...........
...........................
.................o.........
.......o...................
...........................
....o......................

Common rules

• All lines of the map must have the same length (M).
• N ≥ 1, M ≥ 1.
• Strict error handling: invalid format, invalid characters, lines of different lengths, inconsistent N, empty file, etc.

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✅ Expected output

The same map, with the largest square filled with <full> (or x depending on the variant), printed to standard output, followed by a final \n.

Example (Epitech variant, square filled with x)

...........................
....o......................
......................o....
...............o...........
........xxxxxxx............
........xxxxxxx.o..........
.......oxxxxxxx............
........xxxxxxx............
....o......................

On error: print map error\n to standard error and return a non‑zero exit code.

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🚀 Compilation & execution

Makefile

Standard targets:

• make / make all: build bsq
• make clean: remove objects
• make fclean: remove binaries & objects
• make re: fclean + recompile