二、阅读程序（程序三）

#include <bits/stdc++.h>
using namespace std;

#define N 105
#define INF 1e9

int dis1[N][N], dis2[N][N];
int mp[N][N], n, m;

void fun1(int dis[N][N]) {
    static bool vis[N];
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            dis[i][j] = mp[i][j];
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) vis[j] = 0;
        for (int k = 1; k <= n; k++) {
            int now = 0;
            for (int j = 1; j <= n; j++) {
                if (!vis[j] && (!now || dis[i][now] > dis[i][j]))
                    now = j;
            }
            vis[now] = 1;
            for (int j = 1; j <= n; j++) {
                if (!vis[j] && dis[i][j] > dis[i][now] + mp[now][j]) {
                    dis[i][j] = dis[i][now] + mp[now][j];
                }
            }
        }
    }
}

void fun2(int dis[N][N]) {
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            dis[i][j] = mp[i][j];
        }
    }
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            for (int k = 1; k <= n; k++) {
                dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
            }
        }
    }
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (i == j) mp[i][j] = 0;
            else mp[i][j] = INF;
        }
    }
    for (int i = 1; i <= m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        mp[u][v] = w;
    }
    fun1(dis1);
    fun2(dis2);
    int ans = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (dis1[i][j] != dis2[i][j])
                ans++;
        }
    }
    cout << ans << endl;
    return 0;
}

输入满足 $1\le n\le 100$，$1\le m\le \frac{n(n-1)}2$；只保证不存在重边，即不存在 $(u_i,v_i)=(u_j,v_j)$（$i ≠ j$）；边权 $w_i\in[1,10^6]$。如果 $u$ 到 $v$ 不可达，则认为距离为 INF。

29. 程序输出可能为 1。（ ）

{{ select(1) }}

• 正确
• 错误