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Q10973.java
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Q10973.java
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/**
* Date: 16/11/2018
* Author: inhyuck | https://github.com/inhyuck
* Solution URL: https://github.com/inhyuck/problem-solving
* Title: 이전 순열
* description: 1부터 N까지의 수로 이루어진 순열이 있다. 이때, 사전순으로 바로 이전에 오는 순열을 구하는 프로그램을 작성하시오.
* Solution Key: Brute Force
* Problem URL: https://www.acmicpc.net/problem/10973
*/
package io.inhyuck.brute_force;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;
public class Q10973 {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(reader.readLine());
int[] numbers = new int[n];
StringTokenizer tokenizer = new StringTokenizer(reader.readLine());
for (int i = 0; i < n; i++) {
numbers[i] = Integer.parseInt(tokenizer.nextToken());
}
boolean hasPrevPermutation = prevPermutation(numbers);
if (!hasPrevPermutation) {
System.out.println("-1");
return;
}
StringJoiner joiner = new StringJoiner(" ");
Arrays.stream(numbers).forEach(x -> joiner.add(Integer.toString(x)));
System.out.println(joiner.toString());
}
private static boolean prevPermutation(int[] numbers) {
for (int i = numbers.length - 1; i > 0; i--) {
if (numbers[i] < numbers[i - 1]) {
swap(numbers, i - 1, getSwapNumber(numbers, i, numbers[i - 1]));
reverseArray(numbers, i, numbers.length - 1);
return true;
}
}
return false;
}
private static void reverseArray(int[] numbers, int fromIndex, int toIndex) {
int length = toIndex - fromIndex + 1;
for (int i = 0; i < length / 2; i++) {
swap(numbers, fromIndex + i, toIndex - i);
}
}
private static int getSwapNumber(int[] numbers, int index, int preValue) {
for (int i = numbers.length - 1; i > index; i--) {
if (numbers[i] < preValue) {
return i;
}
}
return index;
}
private static void swap(int[] numbers, int a, int b) {
int temp = numbers[a];
numbers[a] = numbers[b];
numbers[b] = temp;
}
}