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