DiffK - facebook code lab - study the solution provided by the lab

DiffK1.cpp

class Solution {
    public:
        bool diffPossible(vector<int> &num, int diff) {
            if (num.size() < 2 || diff < 0) return false;
            int j = 0, len = num.size();
            for (int i = 0; i < len - 1; i++) {
                j = max(j, i + 1);
                while (j < len && num[j] - num[i] < diff) j += 1;
                if (j < len && num[j] - num[i] == diff) return true;
            }
            return false;
        }
};