7. kotprog, "tisztitott" verzio

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

#define INPUT_FILE      "be.txt"
#define OUTPUT_FILE     "ki.txt"
#define MAX_WORD_SIZE   200

char *encode(const char *str, const int *key, int cols);
char *decode(const char *str, const int *key, int cols);

int main() {
    FILE *in = fopen(INPUT_FILE, "r");

    int func, cols;
    fscanf(in, "%d %d", &func, &cols);

    int key[10];
    int i;
    for (i = 0; i < cols; i++) {
        fscanf(in, "%d", &key[i]);
    }

    char *str = (char *) malloc(sizeof(char) * MAX_WORD_SIZE + 1);
    fscanf(in, "%s", str);

    if (func == 1) {
        str = encode(str, key, cols);
    } else {
        str = decode(str, key, cols);
    }

    FILE *out = fopen(OUTPUT_FILE, "w");
    fprintf(out, "%s\n", str);
    fclose(out);
}

char *encode(const char *str, const int *key, int cols) {
    int rows = strlen(str) / cols;
    char **table = (char **) malloc(sizeof(char *) * rows);

    int i, j;
    for (i = 0; i < rows; i++) {
        table[i] = (char *) malloc(sizeof(char) * cols);
        for (j = 0; j < cols; j++) {
            table[i][j] = str[i * cols + j];
        }
    }

    char *coded = (char *) malloc(sizeof(char) * strlen(str) + 1);
    for (i = 0; i < cols; i++) {
        for (j = 0; j < rows; j++) {
            coded[i * rows + j] = table[j][key[i] - 1];
        }
    }
    coded[strlen(str)] = '\0';
    return coded;
}

char *decode(const char *str, const int *key, int cols) {
    int rows = strlen(str) / cols;
    char **table = (char **) malloc(sizeof(char *) * cols);

    int i, j;
    for (i = 0; i < cols; i++) {
        table[key[i]] = (char *) malloc(sizeof(char) * rows + 1);
        for (j = 0; j < rows; j++) {
            table[key[i]][j] = str[i * rows + j];
        }
    }

    char *decoded = (char *) malloc(sizeof(char) * strlen(str) + 1);
    for (j = 0; j < rows; j++) {
        for (i = 1; i <= cols; i++) {
            decoded[j * cols + i - 1] = table[i][j];
        }
    }
    decoded[strlen(str)] = '\0';

    return decoded;
}