Used a hashset to identify duplicates and marked the duplicate with -1, then moved the distinct elements to left most Used slow and fast pointers to identify the cycle Used a recursive algorithm by keeping track of min and max values to validate binary dree Design DEsigned a robust approach to reduce latency and cached the most frequently requested result, replicated the database to handle db failure (Master - Slave Architecture), CDN to serve static content, Gateway and loadbalancer to route request to available server instances and sigle point of entry.