#include <iostream> #include <cstring> using namespace std; const int N = 1000010; int n, m, s, t; bool st[N]; int h[N], e[N], w[N], ne[N], idx; int d[N]; void add(int u, int v, int weight) { e[idx] = v, w[idx] = weight, ne[idx] = h[u], h[u] = idx ++; } int dijkstra() { memset(d, 0x3f, sizeof d); d[s] = 0; for (int i = 0; i < n; i ++ ) { int t = -1; for (int j = 1; j <= n; j ++ ) if (!st[j] && (t == -1 || d[t] > d[j])) t = j; st[t] = true; for (int j = h[t]; j != -1; j = ne[j]) { int k = e[j]; if (d[k] > d[t] + w[j]) d[k] = d[t] + w[j]; } } return d[t]; } int main() { cin >> n >> m >> s >> t; memset(h, -1, sizeof h); while (m -- ) { int u, v, weight; cin >> u >> v >> weight; add(u, v, weight); add(v, u, weight); } cout << dijkstra() << endl; return 0; }这段代码用scanf替代cin

您使用scanf来替代cin，以下是修改后的代码示例：

#include <cstdio>
#include <cstring>
using namespace std;

const int N = 1000010;
int n, m, s, t;
bool st[N];
int h[N], e[N], w[N], ne[N], idx;
int d[N];

void add(int u, int v, int weight)
{
    e[idx] = v, w[idx] = weight, ne[idx] = h[u], h[u] = idx ++;
}

int dijkstra()
{
    memset(d, 0x3f, sizeof d);
    d[s] = 0;

    for (int i = 0; i < n; i ++ )
    {
        int t = -1;
        for (int j = 1; j <= n; j ++ )
            if (!st[j] && (t == -1 || d[t] > d[j]))
                t = j;

        st[t] = true;

        for (int j = h[t]; j != -1; j = ne[j])
        {
            int k = e[j];
            if (d[k] > d[t] + w[j])
                d[k] = d[t] + w[j];
        }
    }

    return d[t];
}

int main()
{
    scanf("%d%d%d%d", &n, &m, &s, &t);
    memset(h, -1, sizeof h);
    while (m -- )
    {
        int u, v, weight;
        scanf("%d%d%d", &u, &v, &weight);
        add(u, v, weight);
        add(v, u, weight);
    }

    printf("%d\n", dijkstra());

    return 0;
}

注意，scanf函数的用法与cin不同，需要指定输入的变量类型，并且需要使用&符号获取变量的地址。另外，输出时需要使用printf函数。