【链接】
【题意】让你在n个数字中再加入一个数字 使得这n+1个数字排序之后 相邻两个数字的差都相同
【题解】
注意相邻为0的情况 这种情况 只有全都相同才行 只有一种情况 然后就是样例里的a[i]-a[i-1]只有两种数字 然后较小的a[i]-a[i-1]有n-2个,较大的a[i]-a[i-1]有1个,然后较大的是较小的两倍 注意这些细节就好了
【代码】
import java.io.*;import java.util.*;public class Main { static InputReader in; static PrintWriter out; public static void main(String[] args) throws IOException{ //InputStream ins = new FileInputStream("E:\\rush.txt"); InputStream ins = System.in; in = new InputReader(ins); out = new PrintWriter(System.out); //code start from here new Task().solve(in, out); out.close(); } static int N = (int)1e5; static class Task{ int n; int a[] = new int[N+10]; HashMap dic = new HashMap<>(); public void solve(InputReader in,PrintWriter out) { n = in.nextInt(); for (int i = 1;i <= n;i++) a[i] = in.nextInt(); Arrays.sort(a, 1,n+1); if (n==1) { out.println(-1); }else if (n==2) { if (a[1]==a[2]) { out.println(1); out.println(a[1]); }else { if ( (a[1]+a[2])%2==0) { int temp = a[2]-a[1]; out.println(3); out.print((a[1]-temp)+" "+((a[1]+a[2])/2)+" "+(a[2]+temp) ); }else { int temp = a[2]-a[1]; out.println(2); out.println((a[1]-temp)+" "+(a[2]+temp)); } } }else { int temp = a[2]-a[1]; boolean ok = true; for (int i = 3;i <= n;i++) { if (a[i]-a[i-1]!=temp) { ok = false; } } if (ok) { if (temp==0) { out.println(1); out.println(a[1]); }else { out.println(2); out.println((a[1]-temp)+" "+(a[n]+temp)); } }else { for (int i = 2;i <= n;i++) { if (dic.containsKey(a[i]-a[i-1])) { int x = dic.get(a[i]-a[i-1]); dic.put(a[i]-a[i-1],x+1); }else { dic.put(a[i]-a[i-1], 1); } } if (dic.size()>2) { out.println(0); }else { Iterator it = dic.keySet().iterator(); int temp1 = (int)it.next(); int temp2 = (int)it.next(); if (temp1>temp2) { int xx = temp1;temp1 = temp2;temp2 = xx; } if ( (temp2 == temp1*2) && ( (int)dic.get(temp2) )==1 ) { out.println(1); for (int i = 2;i <= n;i++) { if (a[i]-a[i-1]==temp2) { out.println(a[i-1]+temp1); } } }else { out.println(0); } } } } } } static class InputReader{ public BufferedReader br; public StringTokenizer tokenizer; public InputReader(InputStream ins) { br = new BufferedReader(new InputStreamReader(ins)); tokenizer = null; } public String next(){ while (tokenizer==null || !tokenizer.hasMoreTokens()) { try { tokenizer = new StringTokenizer(br.readLine()); }catch(IOException e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } public int nextInt() { return Integer.parseInt(next()); } }}