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AQY_1.java
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package BiShi.AQY;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;
public class AQY_1 {
public static ArrayList<ArrayList<Integer>> permutation(int N,int[] nums){
ArrayList<ArrayList<Integer>> list=new ArrayList<>();
int[] arr=new int[N];
for(int i=1;i<=N;i++){
arr[i-1]=i;
}
helper(arr,0,list,nums);
return list;
}
public static boolean check(int[] arr,int[] nums){
for (int i = 0; i <nums.length ; i++) {
if((nums[i]==1)&&arr[i]<arr[i+1]){
return false;
}
if((nums[i]==0)&&arr[i]>arr[i+1]){
return false;
}
}
return true;
}
public static void helper(int[] arr,int start,ArrayList<ArrayList<Integer>> list,int[] nums) {
if((start==arr.length-1)&&check(arr,nums)){
ArrayList<Integer>tmp=new ArrayList<>();
for(int i=0;i<arr.length;i++){
tmp.add(arr[i]);
}
list.add(tmp);
}else{
for(int i=start;i<arr.length;i++){
int tmp=arr[start];
arr[start]=arr[i];
arr[i]=tmp;
helper(arr,start+1,list,nums);
arr[i]=arr[start];
arr[start]=tmp;
}
}
}
public static void main(String[] args) throws FileNotFoundException {
Scanner sc=new Scanner(new File("/home/mao/workspace/java/src/BiShi/AQY/test1"));
//Scanner sc=new Scanner(System.in);
while (sc.hasNext()){
int N=sc.nextInt();
int[] nums=new int[N-1];
for (int i = 0; i <N-1 ; i++) {
nums[i]=sc.nextInt();
}
ArrayList<ArrayList<Integer>> p=permutation(N,nums);
System.out.println(p.size());
}
}
}