【链接】 我是链接,点我呀:)
【题意】

每个节点的度数不超过k
让你重构一个图
使得这个图满足 从某个点开始到其他点的最短路满足输入的要求

【题解】

把点按照dep的值分类
显然只能由dep到dep+1连边
设cnt[dep]表示到起点的距离为dep的点的集合
如果cnt[dep].size>cnt[dep+1].size
那么只要把dep层的前cnt[dep+1].size个点和dep+1层的点连就好了
否则
只能让dep层的点每个多连几个dep+1层的点了

【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 herenew Task().solve(in, out);out.close();}static int N = (int)1e5;static class Task{class Pair{int x,y;public Pair(int x,int y) {this.x = x;this.y = y;}}int n,k;ArrayList<Integer> g[] = new ArrayList[N+10];ArrayList<Pair> ans = new ArrayList<>();public void solve(InputReader in,PrintWriter out) {for (int i = 0;i <= N;i++) g[i]=new ArrayList<Integer>(); n = in.nextInt();k = in.nextInt();for (int i = 1;i <= n;i++) {int d;d = in.nextInt();g[d].add(i);}if ((int)g[0].size()>1) {out.println(-1);}else {for (int i = 1;i <= n;i++)if ((int)g[i].size()>0 && g[i-1].isEmpty()) {out.println(-1);return;}for (int i = 1;i <= n;i++) {if (g[i].isEmpty()) break;int x = g[i].size();int y = g[i-1].size();//out.println(x+" "+y);if (y>=x) {for (int j = 0;j < x;j++) {ans.add(new Pair(g[i-1].get(j),g[i].get(j)));}int ma = 1;if (i-1>=1) {ma = 2;}if (ma>k) {out.println(-1);return;}}else {//y<xint need = x/y;if (x%y!=0) need++;int ma = need;//out.println(ma);if (i-1>=1) ma++;if (ma>k) {out.println(-1);return;}for (int j = 0;j < x;j++) {int now = j;now = now % y;ans.add(new Pair(g[i-1].get(now),g[i].get(j)));}}}out.println((int)ans.size());for (int i = 0;i < ans.size();i++) {out.println(ans.get(i).x+" "+ans.get(i).y);}}}}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());}}
}