add some notes

chapter10/README.md

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+# Approximation algorithm
+
+-   Easy to write, fast to run, useful for obtaining approximate solutions for NP-hard problems.

chapter11/README.md

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+# Dynamic Programming
+
+A programming technique for decomposing a problem into smaller discrete subproblems.
+
+-   Useful when trying to optimize something given a constraint.
+    -   Example, items in a knapsack of size W that gives the greates value.

chapter12/README.md

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+# K-Nearest Neighbours
+
+Useful for classification, regression and feature extraction. By examining a data point against its K nearest neighbours we can:
+
+-   categorize into a group
+-   predict responses
+-   convert the item into a list of features
+
+A good starting point for machine learning.

chapter4/binary.py

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 import logging
 import random
-import time
 
 logging.basicConfig(level=logging.DEBUG)
 logger = logging.getLogger(__name__)

chapter9/README.md

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+# Shortest path for weighted graph (cost associated edges)
+
+-   Dijkstra's algorithm works when all weights are non-negative
+    -   If there are negative weights use Bellman-Ford.
+-   Priority queue + min heap is optimal when compared to a function that operates on a list.