Language: C++

#include<stdio.h>
#define ERROR -1
 
void fl(int M,int dp[M][M]);
 
int next_perm(int *p, int n)
{
  int i, j, k, tmp;
  /* 上位桁のほうが下位桁よりも小さいところまで移動 */
  for(i = n - 1; i > 0 && p[i-1] >= p[i]; i--);
  /* pが最大(次の並べ替えがない) */
  if(i == 0) return 0;
  /* p[i-1]より値の大きい最も下位の桁をp[j]とする */
  for(j = n - 1; j > i && p[i-1] >= p[j]; j--);
  /* p[i-1]とp[j]とを交換 */
  tmp = p[i-1], p[i-1] = p[j], p[j] = tmp;
  /* p[i]から最下位までを逆順 */
  for(k = 0; k <= ((n-1)-i)/2; k++)
    tmp = p[i+k], p[i+k] = p[(n-1)-k], p[(n-1)-k] = tmp;
  return 1;
}
 
int main(){
	int N,M,R;//N=街の数 M=道の数 R=訪れる街の数
	int i,j;//ループ用変数
	scanf("%d %d %d",&N,&M,&R);
	if(N<2||N>200)return ERROR;
	if(M<1||M>N*(N-1)/2)return ERROR;
	if(R<2||R>8||R>N)return ERROR;
	int res=0,res_tmp[100001],R_ka=1;
	int R_num[R];
	long dist[M];//キョリ
	long d[N][N];//どこからどこへ？のキョリ格納用
	int a,b,tmp;//一時変数
 
	for(i=1;i<N+1;i++){
		for(j=1;j<N+1;j++){
			d[i][j]=100001;
		}
	}
 
	if(N<R)return ERROR;
	for(i=0;i<R;i++){
		scanf("%d ",&R_num[i]);
	}
	for(i=0;i<M;i++){
		scanf("%d %d %d",&a,&b,&dist[i]);
		if(a==b||a==0||b==0||dist==0)return ERROR;
		d[a][b]=dist[i];//ex:a=1,b=2,dist=2→d[1][2]=2
	}
	for(i=1;i<N+1;i++){
		for(j=1;j<N+1;j++){
			if(d[i][j]!=100001&&d[j][i]==100001){
				d[j][i]=d[i][j];
			}
			else if(d[i][j]!=100001&&d[j][i]!=100001){
				if(d[i][j]>d[j][i]){
					d[i][j]=d[j][i];
				}else{
					d[j][i]=d[i][j];
				}
			}
		}
	}
 
	/*for(i=1;i<=N;i++){
		for(j=1;j<=N;j++){
			printf("%dと%dの最短距離＝%d\n",i,j,d[i][j]);
		}
	}*/
	fl(N,d);
    for(i=1;i<N+1;i++){
    	for(j=1;j<N+1;j++){
			if(d[i][j]==100001){
				d[i][j]=-1;
			}
			if(i==j){
				d[i][i]=-1;
			}
    	}
    }
 
    for(i=R;i!=1;i--){
    	R_ka=i*R_ka;
    }
    int cnt=0;
    //printf("R!=%d\n",R_ka);
    for(j=0;j<R_ka;){
    	  /* 並べ替え */
    	  do {
    		  res=0;
    		  for(i=0;i<R-1;i++){
    			  res+=d[R_num[i]][R_num[i+1]];
    			  /*for(tmp=0;tmp<R;tmp++){
    				  printf("%d",R_num[tmp]);
    			  }printf("\n");*/
    		  }
    		 // printf("res=%d\n",res);
   			res_tmp[j]=res;
   			j++;
   			cnt++;
   			if(cnt==R_ka)break;
    	  } while(next_perm(R_num, R));
		/*for(i=0;i<R-1;i++){
			res+=d[R_num[i]][R_num[i+1]];
		}*/
		/*tmp=R_num[0];
		for(i=0;i<R;i++){
			if(i==R-1){
				R_num[i]=tmp;
			}else{
				R_num[i]=R_num[i+1];
			}
		}*/
    }
	/*for(i=1;i<=N;i++){
		for(j=1;j<=N;j++){
			printf("%dと%dの最短距離＝%d\n",i,j,d[i][j]);
		}
	}*/
   // printf("cnt=%d\n",cnt);
    res=100001;
    for(i=0;i<R_ka;i++){
    	if(res>res_tmp[i]){
    		res=res_tmp[i];
    	}
    }
    /*for(i=0;i<R_ka;i++){
    	printf("res_tmp=%d\n",res_tmp[i]);
    }*/
    printf("%d\n",res);
    return 0;
}
 
void fl(int M,int dp[M][M]){
	int i,j,k;
    for (k = 1; k < M+1; k++) {
      for (j = 1; j < M+1; j++) {
    	  for(i=1;i<M+1;i++){
			if (dp[i][j] > dp[i][k] + dp[k][j]){
			  dp[i][j] = dp[i][k] + dp[k][j];
			}
        }
      }
    }
}

Compiler output:
a.cc:4:23: error: use of parameter outside function body before ']' token
    4 | void fl(int M,int dp[M][M]);
      |                       ^
a.cc:4:26: error: use of parameter outside function body before ']' token
    4 | void fl(int M,int dp[M][M]);
      |                          ^
a.cc:135:23: error: use of parameter outside function body before ']' token
  135 | void fl(int M,int dp[M][M]){
      |                       ^
a.cc:135:26: error: use of parameter outside function body before ']' token
  135 | void fl(int M,int dp[M][M]){
      |                          ^
a.cc: In function 'void fl(...)':
a.cc:137:21: error: 'M' was not declared in this scope
  137 |     for (k = 1; k < M+1; k++) {
      |                     ^
a.cc:140:29: error: 'dp' was not declared in this scope
  140 |                         if (dp[i][j] > dp[i][k] + dp[k][j]){
      |                             ^~