50111. Hamiltonian Cycle
難度：3/5
意外寫起來很順手（？） 記得排列的時候要順便把有沒有存在路徑先找出來g[i][last] == 0剪掉。
Second Try: 3/5 Used Time 7:311
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42#include <stdio.h>
#include <stdlib.h>
int n, e;
char g[1024][1024] = {0};
int dfs(int arr[], int vis[], int now_cnt){
if(now_cnt == n){
for(int i = 0; i < n; i++){
printf("%d ", arr[i]);
}
printf("%d\n", arr[0]);
return 1;
}
int last = -1;
if(now_cnt != 0) last = arr[now_cnt - 1];
for(int i = 0; i < n; i++){
if(last != -1 && (vis[i] == 1 || g[i][last] == 0)) continue;
if(now_cnt == n - 1 && g[i][arr[0]] == 0) continue;
arr[now_cnt] = i, vis[i] = 1;
int rtv = dfs(arr, vis, now_cnt + 1);
if(rtv) return 1;
arr[now_cnt] = -1, vis[i] = 0;
}
return 0;
}
int main(){
scanf("%d %d", &n, &e);
for(int i = 0; i < e; i++){
int a, b; scanf("%d %d", &a, &b);
g[a][b] = 1;
g[b][a] = 1;
}
int arr[1024] = {0};
int vis[1024] = {0};
int rtv = dfs(arr, vis, 0);
if(rtv == 0) printf("NO SOLUTION\n");
}