NATO2.c

// CS1010 AY2015/6 Semester 2 PE2 Ex2
//
// nato.c
//
// Name:
// Matriculation number:
// plab-id:
// Discussion group:
// Description:

#include <stdio.h>
#include <string.h>
#define MAXLEN 101

int decrypt(char[]);

int main(void)
{
    char name[MAXLEN];
    int len;

    printf("Enter name in NATO alphabet: ");
    fgets(name, MAXLEN, stdin);
    // scanf("%s", name);
    len = strlen(name);

    if(name[len - 1] == '\n')
        name[len - 1] = '\0';

    if(decrypt(name))
        printf("Decrypted name: %s\n", name); // Incomplete
    else
        printf("The given name cannot be decrypted.\n");

    return 0;
}

int decrypt(char name[])
{
    // Do not change this 2D array
    // alphabet[0] -> code word for 'A'
    // alphabet[1] -> code word for 'B'
    // ...
    char alphabet[26][MAXLEN] = { "ALFA", "BRAVO", "CHARLIE", "DELTA", "ECHO", "FOXTROT", "GOLF", "HOTEL", "INDIA",
        "JULIETT", "KILO", "LIMA", "MIKE", "NOVEMBER", "OSCAR", "PAPA", "QUEBEC", "ROMEO", "SIERRA", "TANGO", "UNIFORM",
        "VICTOR", "WHISKEY", "XRAY", "YANKEE", "ZULU" };
    int i, j, k = 0, len, current = 0;
    while(name[current] != '\0') {
        for(i = 0; i < 26; i++) {
            if(name[current] == alphabet[i][0]) {
                len = strlen(alphabet[i]);
                for(j = 1; j < len; j++) {
                    current++;
                    if(name[current] != alphabet[i][j]) {
                        return 0;
                    }
                }
                name[k] = alphabet[i][0];
                k++;
                current++;
                break;
            }
        }
    }
    name[k] = '\0';
    return 1;
}

// Hint 1: For an encryted name starting with a particular
// character (e.g., 'C'), which row of alphabet shows the
// expected code word?

// Hint 2: It is advisable to create a new array for storing
// the (partially) decrypted name and only copy the decryted
// name back to name[] in the end.

// Hint 3: String functions may be useful but they are not
// critical for solving this problem. If you know arrays well,
// you will be able to come up with a good solution.

// Hint 4: Think carefully before starting to code. If you have
// a good solution, you may only need to add ~20 lines of code to
// decrypt().