Graph-Coloring.cpp

#include <stdio.h>
#include <string.h>
int map[101][101], mt[101];
int tmp[101], Ans[101], maxL;
int cant[101];
int T, n, m;
void DFS(int node, int choose, int notchoose) {
 if(choose + notchoose == n || node == n+1) { 
  if(choose > maxL) {
   maxL = choose;
   int i;
   for(i = 0; i < maxL; i++)
    Ans[i] = tmp[i];
  }
  return;
 }  

 if(cant[node] == 0) {
  int i, newNot = notchoose;
  int reduce[n], idx = 0;
  for(i = 0; i < mt[node]; i++) {
   if(cant[map[node][i]] == 0) {
    cant[map[node][i]] = 1, newNot++;
    reduce[idx++] = map[node][i];
   }
  }
  tmp[choose] = node;
  DFS(node+1, choose+1, newNot);
  for(i = 0; i < idx; i++)
   cant[reduce[i]] = 0;
 }
 DFS(node+1, choose, notchoose+(!cant[node]));
}
int main() {
 int i, x, y;
 scanf("%d", &T);
 while(T--) {
  scanf("%d %d", &n, &m);
  memset(mt, 0, sizeof(mt));
  memset(cant, 0, sizeof(mt));
  for(i = 0; i < m; i++) {
   scanf("%d %d", &x, &y);
   map[x][mt[x]++] = y;
   map[y][mt[y]++] = x;
  }
  maxL = 0;
  DFS(1, 0, 0);
  printf("%d\n", maxL);
  for(i = 0; i < maxL-1; i++)
   printf("%d ", Ans[i]);
  printf("%d\n", Ans[i]);
 }
    return 0;
}