Codility Lesson 2

2_MaxCounters.java

class Solution {
    public int[] solution(int N, int[] A) {
        int[] counters = new int[N];
        int max = 0;
        int absMax = 0;
        
        for (int i=0; i<A.length; i++) {
            if (A[i] == N+1) {
                if ((i < A.length-1 && A[i+1] != N+1) || (i==A.length-1)) {
                    absMax += max;
                    max = 0;
                    counters = new int[N];
                }
            } else {
                counters[A[i]-1]++;
                if (max < counters[A[i]-1])
                    max = counters[A[i]-1];
            }
        }
        
        for (int i=0; i<counters.length; i++)
            counters[i] += absMax;
        
        return counters;
    }
}

2_Missing Integer.java

import java.util.HashMap;

class Solution {
    public int solution(int[] A) {
        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        int max = 0;
        
        for (int i=0; i<A.length; i++) {
            map.put(A[i], 1);
            if (max < A[i])
                max = A[i];
        }
        
        for (int i=1; i<=max; i++)
            if (!map.containsKey(i))
                return i;
        
        return max+1;
    }
}