大佬们帮帮萌新吧

#include <bits/stdc++.h>
using namespace std;
int n, m;
struct node {
	int to, w;
} ;
vector <node> edge[205];
int dis[205][205], rd[205];
vector <int> e[205];
vector <int> mfY;
int vis[205];
inline void build (int x) {
//	cout << x << '\n';
	for (int i = 1; i <= n; i++) {
        e[i].clear();
		rd[i] = 0;
	}
	for (int i = 1; i <= n; i++) {
		if (i == x) continue; 
		for (int j = 0; j < edge[i].size(); j++) { 
			int to = edge[i][j].to, w = edge[i][j].w;
			if (dis[x][to] == dis[x][i] + w) {
				e[i].push_back (to);
//				cout << "\n" << i << " -> " << to << '\n';
				rd[to]++;
			}
		}
	}
	for (int i = 1; i <= n; i++) {
		if (i == x) continue;
		for (int j = 0; j < e[i].size(); j++) { 
			int to = e[i][j];
			if (rd[to] == 1) {
				mfY.push_back (i); 
			}
		}
	}
}
int main () {
	scanf ("%d%d", &n, &m);
	memset (dis, 0x3f, sizeof (dis)); 
	for (int i = 1; i <= n; i++) dis[i][i] = 0;
	for (int i = 1; i <= m; i++) {
		int x, y, w;
		scanf ("%d%d%d", &x, &y, &w);
		dis[x][y] = w;
		dis[y][x] = w;
		edge[x].push_back ({y, w});
		edge[y].push_back ({x, w});
	}
	for (int k = 1; k <= n; k++) {
		for (int i = 1; i <= n; i++) {
			for (int j = 1; j <= n; j++) {
				if (dis[i][k] != 0x3f3f3f3f && dis[k][j] != 0x3f3f3f3f && dis[i][k] + dis[k][j] < dis[i][j]) {
					dis[i][j] = dis[i][k] + dis[k][j];
				}
			}
		}
	}
	int flag = 0;
	for (int dot = 1; dot <= n; dot++) {
		mfY.clear();
		build (dot);
//		cout<<dot<<":"<<endl;
		for (int i = 0; i < mfY.size(); i++) {
			flag = 1;
//			cout << mfY[i] << ' ';
			vis[mfY[i]] = 1;
		}
//		cout <<endl;
	}
	for (int i = 1; i <= n; i++) {
		if (vis[i]) {
			printf ("%d ", i);
		}
	}
	if (flag == 0) {
		printf ("No important cities.");
	}
	return 0;
}