BigOExample.java

package ch05;

public class BigOExample {
 public int O_1(int n) {
 return 42;
 }

 public int O_logn(int n) {
 while (n > 1)
 n /= 2;
 return n;
 }

 public int O_n(int n) {
 int r = 0;
 for (int i = 0; i < n; i++)
 r++;
 return r;
 }

 public int O_nlogn(int n) {
 int r = n;
 for (int i = 0; i < n; i++) {
 while (n > 1)
 n /= 2;
 n = r;
 }
 return r;
 }

 public int O_n2(int n) {
 int r = 0;
 for (int i = 0; i < n; i++) {
 for (int j = 0; j < n; j++)
 r += j;
 }
 return r;
 }

 public int O_2n(int n) {
 if (n <= 1)
 return n;
 else
 return O_2n(n - 1) + O_2n(n - 2);
 }

 public int O_nfact(int n) {
 for (int i = 0; i < n; i++) {
 O_nfact(n - 1);
 }
 return n;
 }

 static int count = 0;

 static public int factorial(int n) {
 if (n >= 1) {
 count++;
 return n * factorial(n - 1);
 } else {
 count++;
 return 1;
 }
 }

 public static void main(String[] args) {
 count = 0;
 factorial(5);
 System.out.printf("factorial(5), count = %d\n", count);
 count = 0;
 factorial(6);
 System.out.printf("factorial(6), count = %d\n", count);
 count = 0;
 factorial(7);
 System.out.printf("factorial(7), count = %d\n", count);
 }
}