encodedmessage

E.ans

TOPSECRET
RosesAreRedVioletsAreBlue
SquaresMayBeEven

E.in

3
RSTEEOTCP
eedARBtVrolsiesuAoReerles
EarSvyeqeBsuneMa

encodedmessage.c

#include <stdio.h>
#include <string.h>
#include <math.h>

#define BUFFER_SIZE (10001)

unsigned int transform(unsigned int n, unsigned int row_length)
{
    unsigned int input_row = n / row_length;
    unsigned int input_col = n % row_length;

    unsigned int output_row = row_length - input_col - 1;
    unsigned int output_col = input_row;

    return output_row * row_length + output_col;
}

int main(int argc, char ** argv)
{
    unsigned int number_of_test_cases;
    scanf("%i", &number_of_test_cases);

    int i;
    for(i = 0; i < number_of_test_cases; ++i)
    {
        char input_buffer[BUFFER_SIZE];
        scanf("%s", input_buffer);
        unsigned int input_length = strlen(input_buffer);
        char output_buffer[input_length+1];

        unsigned int row_length = (int)floor(sqrt(input_length));
        int j;
        for(j = 0; j < input_length; ++j)
        {
            output_buffer[transform(j, row_length)] = input_buffer[j];
        }

        output_buffer[input_length] = 0;
        printf("%s\n", output_buffer);
    }

    return 0;
}

Makefile

C=gcc
C_FLAGS=-g -Wall -O3

.PHONY: test submit clean

default: test

test: encodedmessage
	./encodedmessage < E.in | diff E.ans -

encodedmessage: encodedmessage.c
	$(C) $(C_FLAGS) $^ -o $@ -lm

submit:
	kattis -f -p encodedmessage encodedmessage.c

clean:
	rm -f encodedmessage