순열 - 순서가 있는 열
import java.util.Scanner;
public class Permutation {
private static boolean[] isSelected;
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int N = scanner.nextInt();
int R = scanner.nextInt();
isSelected = new boolean[N];
String[] target = new String[N];
for (int i = 0; i < target.length; i++) {
target[i] = scanner.next();
}
permutation(target, R, 0, new StringBuilder());
System.out.println();
permutationRepetition(target, R, 0, new StringBuilder());
}
private static <T> void permutation(T[] target, int R, int count, StringBuilder sb) {
if (count == R) {
System.out.println(sb);
return;
}
for (int i = 0; i < target.length; i++) {
if (!isSelected[i]) {
isSelected[i] = true;
int currentLength = sb.length();
sb.append(target[i] + " ");
permutation(target, R, count + 1, sb);
sb.setLength(currentLength);
isSelected[i] = false;
}
}
}
private static <T> void permutationRepetition(T[] target, int R, int count, StringBuilder sb) {
if (count == R) {
System.out.println(sb);
return;
}
for (int i = 0; i < target.length; i++) {
int currentLength = sb.length();
sb.append(target[i] + " ");
permutationRepetition(target, R, count + 1, sb);
sb.setLength(currentLength);
}
}
}
조합 - 순서가 없는 열
import java.util.Scanner;
public class Combination {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int N = scanner.nextInt();
int R = scanner.nextInt();
String[] target = new String[N];
for (int i = 0; i < target.length; i++) {
target[i] = scanner.next();
}
combination(target, 0, R, 0, new StringBuilder());
System.out.println();
combinationRepetition(target, 0, R, 0, new StringBuilder());
}
private static <T> void combination(T[] target, int start, int R, int count, StringBuilder sb) {
if (count == R) {
System.out.println(sb);
return;
}
for (int i = start; i < target.length; i++) {
int currentLength = sb.length();
sb.append(target[i] + " ");
combination(target, i + 1, R, count + 1, sb);
sb.setLength(currentLength);
}
}
private static <T> void combinationRepetition(T[] target, int start, int R, int count, StringBuilder sb) {
if (count == R) {
System.out.println(sb);
return;
}
for (int i = start; i < target.length; i++) {
int currentLength = sb.length();
sb.append(target[i] + " ");
combinationRepetition(target, i, R, count + 1, sb);
sb.setLength(currentLength);
}
}
}
부분집합 - 주어진 원소르 만들 수 있는 모든 경우의 수
import java.util.Scanner;
public class PowerSet {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int N = scanner.nextInt();
String[] target = new String[N];
for (int i = 0; i < target.length; i++) {
target[i] = scanner.next();
}
powerSet(target, 0, new StringBuilder());
}
private static <T> void powerSet(T[] target, int start, StringBuilder sb) {
if (start == target.length) {
System.out.println(sb);
return;
}
int currentLength = sb.length();
sb.append(target[start] + " ");
powerSet(target, start + 1, sb);
sb.setLength(currentLength);
sb.append("X ");
powerSet(target, start + 1, sb);
sb.setLength(currentLength);
}
}