'commit'

TangDou/XiTi/1410.cpp

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+#include <bits/stdc++.h>
+
+using namespace std;
+
+// AcWing 1128 信使【最短路】
+// https://blog.csdn.net/qq_43964401/article/details/109039446
+
+
+const int N = 110;
+int n, m;
+int d[N][N];
+
+#define INF 0x3f3f3f3f
+
+//floyd核心算法
+void floyd() {
+    for (int k = 1; k <= n; k++)
+        for (int i = 1; i <= n; i++)
+            for (int j = 1; j <= n; j++)
+                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
+}
+
+int main() {
+    //输入+输出重定向
+    freopen("../1410.txt", "r", stdin);
+
+    cin >> n >> m;
+
+    //初始化
+    for (int i = 1; i <= n; i++)
+        for (int j = 1; j <= n; j++)
+            if (i == j) d[i][j] = 0;
+            else d[i][j] = INF;
+
+    //输入数据
+    while (m--) {
+        int a, b, c;
+        cin >> a >> b >> c;
+        d[a][b] = c, d[b][a] = c; //双向，无向图
+    }
+    //核心计算
+    floyd();
+
+    //哪条路线最长
+    int res = 0;
+    for (int i = 1; i <= n; i++)
+        res = max(res, d[1][i]);
+
+    //如果有不存在的，就返回-1
+    if (res >= INF) puts("-1");
+    else printf("%d\n", res);
+
+    //关闭文件
+    fclose(stdin);
+    return 0;
+}
+