SoldierRank

Solution.java

class Solution {
    public int solution(int[] ranks) {
        // write your code in Java SE 8
        int sum = 0;
        Set<Integer> soldierRank =  new HashSet<Integer>();
        
        for (int i = 0; i< ranks.length; i++) {
            soldierRank.add(ranks[i]);
        }
        
        for(int k = 0; k < ranks.length; k++){
            if(soldierRank.contains(ranks[k]+1)){
                sum++;
            }
        }
        
        return sum;
    }
}