Here you can find several projects dedicated to the Deep Reinforcement Learning methods.
These projects are developed as part of the Udacity Deep Reinforcement Learning Nanodegree Program.
Several projects are devoted to Deep Reinforcement Learning Architectures, Value-Based Methods and Bellman Equation, Policy-Based Methods, Policy-Gradient Methods and Actor-Critic Methods.

• Monte-Carlo Methods
  In Monte Carlo (MC), we play episodes of the game until we reach the end, we grab the rewards collected on the way
  and move backward to the start of the episode. We repeat this method a sufficient number of times and we average
  the value of each state.
• Temporal Difference Methods and Q-learning
• Reinforcement Learning in Continuous Space (Deep Q-Network)
• Function Approximation and Neural Network
  The Universal Approximation Theorem (UAT) states that feed-forward neural networks containing a
  single hidden layer with a finite number of nodes can be used to approximate any continuous function provided
  rather mild assumptions about the form of the activation function are satisfied.
• Policy-Based Methods, Hill Climbing, Simulating Annealing
  Random-restart hill climbing is a surprisingly effective algorithm in many cases. Simulated annealing is a good probabilistic technique because it does not accidentally think a local extrema is a global extrema.
• Policy-Gradient Methods, REINFORCE, PPO
  Define a performance measure J(\theta) to maximaze. Learn policy paramter \theta throgh approximate gradient ascent.
  
• Actor-Critic Methods, A3C, A2C, DDPG, SAC
  The key difference from A2C is the Asynchronous part. A3C consists of multiple independent agents(networks) with
  their own weights, who interact with a different copy of the environment in parallel. Thus, they can explore
  a bigger part of the state-action space in much less time.

CartPole, Policy Based Methods, Hill Climbing

CartPole, Policy Gradient Methods, REINFORCE

Cartpole, DQN

Cartpole, Double DQN

Markov Decision Process, Monte-Carlo, Gridworld 6x6

Pong, Policy Gradient Methods, PPO

Pong, Policy Gradient Methods, REINFORCE

Project 1: Navigation, Deep-Q-Network, ReplayBuffer

Project 2: Continuous Control-Reacher, DDPG, environment Reacher (Double-Jointed-Arm)

Project 2: Continuous Control-Crawler, PPO, environment Crawler

Project 3: Collaboration_Competition-Tennis, Multi-agent DDPG, environment Tennis

BipedalWalker, Twin Delayed DDPG (TD3)

BipedalWalker, PPO, Vectorized Environment

BipedalWalker, Soft-Actor-Critic (SAC)

BipedalWalker, A2C, Vectorized Environment

CarRacing with PPO, Learning from Raw Pixels

• Pong, 8 parallel agents
• CarRacing, Single agent, Learning from pixels
• C r a w l e r , 12 parallel agents
• BipedalWalker, 16 parallel agents

• CartPole, Policy Based Methods, Hill Climbing

• CartPole, Policy Gradient Methods, REINFORCE

• Cartpole with Deep Q-Learning

• Cartpole with Doouble Deep Q-Learning

• on Policy-Gradient Methods, see 1, 2, 3.
• on REINFORCE, see 1, 2, 3.
• on PPO, see 1, 2, 3, 4, 5.
• on DDPG, see 1, 2.
• on Actor-Critic Methods, and A3C, see 1, 2, 3, 4.
• on TD3, see 1, 2, 3
• on SAC, see 1, 2, 3, 4, 5
• on A2C, see 1, 2, 3, 4, 5

How does the Bellman equation work in Deep Reinforcement Learning?

A pair of interrelated neural networks in Deep Q-Network

• Four BipedalWalker Gaits
• BipedalWalker by Training Stages
• CarRacing by Training Stages