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Author: Lee jeonggeun

.classpath

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

.gitignore

@@ -0,0 +1 @@
+/bin

.project

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>Algorithm</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

README.md

@@ -2,3 +2,12 @@ Algorithm
 =========
 
 Algorithm study
+
+p140910
+Bubble sort
+
+p140913
+Calculate Factorial, Permutation, Combination
+
+p140916
+print weekday at afterDay

src/p140910/Bubble.java

@@ -0,0 +1,74 @@
+package p140910;
+
+/**
+ * bubble sort
+ * 
+ * @author red
+ * 
+ */
+public class Bubble {
+
+	/**
+	 * bubble sort
+	 * @param arr
+	 */
+	public static int bubbleSort(int[] arr) {
+		int cntSwap = 0;
+		boolean swapped;
+		do {
+			swapped = false;
+			for (int i = 1; i < arr.length; i++) {
+				if (arr[i - 1] > arr[i]) {
+					int tmp;
+					tmp = arr[i - 1];
+					arr[i - 1] = arr[i];
+					arr[i] = tmp;
+					swapped = true;
+					cntSwap++;
+				}
+			}
+		}while(swapped);
+		return cntSwap;
+	}
+	
+	/**
+	 * enhanced bubble sort
+	 * @param arr
+	 * @return
+	 */
+	public static int enhancedBubbleSort(int[] arr){
+		int cntSwap = 0;
+		boolean swapped;
+		int lastIndex = arr.length;
+		do{
+			swapped = false;
+			for(int i = 1; i<lastIndex; i++){
+				if(arr[i-1] > arr[i]){
+					int tmp = arr[i-1];
+					arr[i-1] = arr[i];
+					arr[i] = tmp;
+					swapped = true;
+					cntSwap++;
+				}
+			}
+			lastIndex--;
+		}while(swapped);
+		
+		return cntSwap;
+	}
+
+	public static void main(String[] args) {
+		int[] arr = { 3, 4, 16, 2 ,8, 32, 88, 1};
+		for(int a:arr)
+			System.out.print(a+",");
+		System.out.println();
+		int cntSwap;
+		//cntSwap = bubbleSort(arr);
+		cntSwap = enhancedBubbleSort(arr);
+		for(int a:arr)
+			System.out.print(a+",");
+		System.out.println();
+		System.out.println("cntSwap : " + cntSwap);
+	}
+
+}

src/p140913/Combination.java

@@ -0,0 +1,23 @@
+package p140913;
+
+public class Combination {
+
+	/**
+	 * Calculate Combination
+	 * @param n
+	 * @param k
+	 * @return
+	 */
+	public static int comb(int n, int k){
+		// n장에서 k장을 선택하는 모든 순열의 수 / k장을 치환하는 모든 가지의 수.
+		int c = Permutation.perm(n, k) / Permutation.perm(k, k);
+		return c;
+	}
+	public static void main(String[] args) {
+		// what is 5C3
+		// 3개의 카드중에 2개를 선택할 경우의 갯수는? (순서 구별안. {A,B,C} = {C,B,A})
+		int c = comb(5,3);
+		System.out.println(c);
+	}
+
+}

src/p140913/Factorial.java

@@ -0,0 +1,21 @@
+package p140913;
+
+public class Factorial {
+	/**
+	 * Calculate Factorial
+	 * @param n
+	 * @return
+	 */
+	public static int facto(int n){
+		int m = 1;
+		for(int i = n; i >= 1 ; i--){
+			m = m*i;
+		}
+		return m;
+	}
+	public static void main(String[] args) {
+		// what is 7! (7*6*5*4*3*2*1)
+		System.out.println(facto(7));
+	}
+
+}

src/p140913/Permutation.java

@@ -0,0 +1,21 @@
+package p140913;
+
+public class Permutation {
+	/**
+	 * Calculate Permutation
+	 * @param n
+	 * @param k
+	 * @return
+	 */
+	public static int perm(int n, int k){
+		
+		int p = Factorial.facto(n) / Factorial.facto(n - k);
+		return p;
+	}
+	public static void main(String args[]){
+		// what is 3P2
+		// 3개의 카드중에 2개를 선택할 경우의 갯수는? (순서도 구별됨. {A,B,C} != {C,B,A})
+		int p = perm(3,2);
+		System.out.println(p);
+	}
+}

src/p140916/Weekday.java

@@ -0,0 +1,90 @@
+package p140916;
+
+public class Weekday {
+
+	/**
+	 * print weekday at d'after
+	 * @param d
+	 */
+	public void run(int d){
+		int remainDay = d%7;
+		System.out.println(remainDay);
+		
+		switch(remainDay){
+		case 0:
+			System.out.println("sunday");
+			break;
+		case 1:
+			System.out.println("monday");
+			break;
+		case 2:
+			System.out.println("tuesday");
+			break;
+		case 3:
+			System.out.println("wednesday");
+			break;
+		case 4:
+			System.out.println("thursday");
+			break;
+		case 5:
+			System.out.println("friday");
+			break;
+		case 6:
+			System.out.println("saturday");
+			break;
+		}
+		
+	}
+	
+	/**
+	 * print weekday at n-after
+	 * @param n
+	 */
+	public void run2(int n){
+		/*
+		 * 10^0 / 7 = 1
+		 * 10^1 / 7 = 3
+		 * 10^2 / 7 = 2
+		 * 10^3 / 7 = 6
+		 * 10^4 / 7 = 4
+		 * 10^5 / 7 = 5
+		 * 10^6 / 7 = 1
+		 * 10^7 / 7 = 3
+		 * ...
+		 * ... 
+		 */
+		int remainDay = n%6;
+		
+		switch(remainDay){
+		case 0:
+			System.out.println("monday");
+			break;
+		case 1:
+			System.out.println("wednesday");
+			break;
+		case 2:
+			System.out.println("tuesday");
+			break;
+		case 3:
+			System.out.println("saturday");
+			break;
+		case 4:
+			System.out.println("thursday");
+			break;
+		case 5:
+			System.out.println("friday");
+			break;
+		}
+		
+	}
+	public static void main(String[] args) {
+		Weekday wd = new Weekday();
+		
+		// what is weekday at 100day after? 
+		wd.run(100);
+		
+		// what is weekday at 10^100 day after?
+		wd.run(100);
+	}
+
+}