Start to review the basic about sorting from Princeton course. Need to cover mergesort, quicksort, heap.

Author: poweihuang0817

Fundamentals/Sort/Basic_about_Sorting/Lecture_Note_Princeton/Sorting_Introduction_04152018.md

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+# Sorting Introduction
+
+## Interface
+- Generic sort relies on Comparable Interface. 
+- Each type should implement CompareTo. ( Callback mechanism)
+- The CompareTo should follow total order and output negative, 0,plus if it's smaller, equal and larger than the other.
+- Each sort algorithm should target Comparable Interface.

Fundamentals/Sort/Selection_Sort/Java/Selection.java

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+public class Selection
+{
+	public static void sort(Comparable[] a)
+	{
+		int N=a.length;
+		for(int i=0;i<N;i++)
+		{
+			int min=i;
+			for(int j=i+1;j<N;j++)
+			{
+				if(less(a[j],a[min]))
+					min=j;
+			}
+			exch(a,i,min);
+		}
+	}
+
+	private static boolean less(Comparable v, Comparable w)
+	{  return v.compareTo(w) < 0;  }
+	
+	private static void exch(Comparable[] a, int i, int j)
+	{
+		   Comparable swap = a[i];
+		   a[i] = a[j];
+		   a[j] = swap;
+	}
+
+}

Fundamentals/Sort/Selection_Sort/Note/Selection_Sort_04152018.md

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+# Selection Sort
+
+## Mechanism
+- Find the index of min of the remaining entry
+- Swap i and that index.
+
+## Properties of selection sort
+- O(N^2), even if the input is sorted
+- O(N) exchange. Minimum dave movement.
+
+## Complexity
+- N^2/2 compare
+- N exchange