7. kotprog

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

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

int read_error() {
    fprintf(stderr, "Read error!\n");
    return -2;
}

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");
    if (!in) {
        fprintf(stderr, "Can't read \"%s\"!\n", INPUT_FILE);
        return -1;
    }

    int func, cols;
    if (fscanf(in, "%d %d", &func, &cols) != 2) return read_error();

    int key[10];
    size_t i;
    for (i = 0; i < cols; i++) {
        if (fscanf(in, "%d", &key[i]) != 1) return read_error();
    }

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

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

    FILE *out = fopen(OUTPUT_FILE, "w");
    if (!out) {
        fprintf(stderr, "Can't write \"%s\"!\n", OUTPUT_FILE);
        return -3;
    }

    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);

    size_t i, j;
    for (i = 0; i < rows; i++) {
        table[i] = (char *) malloc(sizeof(char) * cols);
        for (j = 0; j < cols; j++) {
            // printf("%c ", str[i * cols + j]);
            table[i][j] = str[i * cols + j];
        }
        // printf("\n");
    }

    char *coded = (char *) malloc(sizeof(char) * strlen(str) + 1);
    for (i = 0; i < cols; i++) {
        // printf("Key: %d\n", key[i]);
        for (j = 0; j < rows; j++) {
            // printf("%d %d %d %c\n", i, j, i * rows + j, table[j][key[i] - 1]);
            coded[i * rows + j] = table[j][key[i] - 1];
        }
    }
    coded[strlen(str)] = '\0';
    //printf("coded: '%s'\n", coded);
    return coded;
}

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

    size_t i, j;
    for (i = 0; i < cols; i++) {
        table[key[i]] = (char *) malloc(sizeof(char) * rows + 1);
        for (j = 0; j < rows; j++) {
            // printf("%d %d %d\n", i, j, key[i]);
            table[key[i]][j] = str[i * rows + j];
            // printf("%c ", table[key[i]][j]);
        }
        // printf("\n");
    }

    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;
}