Dijkstra队列为什么不能只放一个整数？

struct cmp {
	bool operator()(int a, int b) const{
		return dis[b] < dis[a];
	}
};
std::priority_queue<int, std::vector<int>, cmp>q;

#include<bits/stdc++.h>
const int N1 = 1e4 + 3;
const int N2 = 5e5 + 3;
int n, m, s, head[N1],cnt=0;
bool use[N1];
long long dis[N1];
struct edge {
	int to,next;
	long long val;
}edges[N2];
struct cmp {
	bool operator()(int a, int b) const{
		return dis[b] < dis[a];
	}
};
std::priority_queue<int, std::vector<int>, cmp>q;
int main() {
	scanf("%d %d %d", &n, &m, &s);
	std::fill(dis+1,dis+n+1,INT_MAX);
	int u, v, w;
	while (m--) {
		scanf("%d %d %d", &u, &v, &w);
		edges[++cnt].to = v;
		edges[cnt].next = head[u];
		edges[cnt].val = w;
		head[u] = cnt;
	}
	q.push(s);
	dis[s] = 0;
	while (!q.empty()) {
		int now = q.top();
		q.pop();
		if (use[now])continue;
		use[now] = true;
		for (int i = head[now]; i; i = edges[i].next) {
			int to = edges[i].to;
			if (dis[to] > dis[now] + edges[i].val) {
				dis[to] = dis[now] + edges[i].val;
				q.push(to);
			}
		}
	}
	for (int i = 1; i <= n; i++) printf("%lld ", dis[i]);
	return 0;
}