UVa - 10038 - Jolly Jumpers

// Jolly Jumper
// uva 10038
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include <string.h>

#define MAXSIZE 3001

int main()
{
    // record whether the number from 1 to MAXSIZE-1 appeared.
    // the effective index is in [1,(MAXSIZE-1)],
    // so the array size will be MAXSIZE
    bool appeared[MAXSIZE];
    
    int n;                      // how many numbers
    int numbers[MAXSIZE];
    // counter
    int i;
    bool isJolly;
    int difference;
    
    while (scanf("%d", &n) != EOF){
        isJolly = true;
        
        // read numbers
        for (i = 0; i < n; i++){
            scanf(" %d", &numbers[i]);
        }

        memset((appeared + 1), false, n);

        // record number that appeared
        for (i = 1; i < n; i++){
            difference = abs(numbers[i]-numbers[i-1]);
            if (difference >= 1 && difference <= n-1)
                appeared[difference] = true;
        }

        // check Jolly
        for (i = 1; i <= n-1; i++){
            if (appeared[i] == false){
                isJolly = false;
                break;
            }
        }

        printf("%s", (isJolly ? "Jolly\n": "Not jolly\n"));

    }
    return 0;
}