114 lines
2.4 KiB
C++
114 lines
2.4 KiB
C++
#include<iostream>
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#include<vector>
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#include<string.h>
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using namespace std;
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int map[1005][1005];
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int pre[1005];
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int dis[1005];
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bool s[1005];
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class path
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{
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public:
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int start, end;
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};
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vector<path>p;
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void dijkstra(int n)
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{
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memset(s,false,sizeof(s));
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int i, j, k;
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for (i = 2; i <= n; i++)
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{
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dis[i] = map[1][i];
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if (map[1][i] != -1)
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{
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pre[i] = 1;
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}
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else
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{
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pre[i] = -1;
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}
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}
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pre[1] = -1;
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dis[1] = 0;
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s[1] = true;
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for (j = 2; j <= n; j++)
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{
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int min = 100000;
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int u;
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for (i = 1; i <= n; i++)
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{
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if (!s[i] && dis[i] != -1)
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{
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if (min > dis[i])
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{
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min = dis[i];
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u = i;
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}
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}
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}
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s[u] = true;
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for (k = 1; k <= n;k++)
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{
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if (!s[k] && map[u][k]!=-1)
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{
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if ((dis[k] > dis[u] + map[u][k])||dis[k]==-1)
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{
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dis[k] = dis[u] + map[u][k];
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pre[k] = u;
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}
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}
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}
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}
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}
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void findpath(int n)
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{
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p.clear();
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int i = n;
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while (pre[i]!=-1)
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{
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path tmp;
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tmp.start = pre[i];
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tmp.end = i;
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p.push_back(tmp);
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i=pre[i];
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}
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}
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int main()
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{
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int n, m;
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while (cin>>n>>m)
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{
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int i,k;
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int start, end, weight;
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for (i = 1; i <= n;i++)
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for (k = 1; k <= n; k++)
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{
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map[i][k] = -1;
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}
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for (i = 0; i < m; i++)
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{
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cin >> start >> end >> weight;
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map[start][end] = weight;
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map[end][start] = weight;
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}
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dijkstra(n);
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findpath(n);
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int num,max=-1;
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for (num = 0; num < p.size(); num++)
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{
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path tmp = p[num];
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int t;
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t = map[tmp.start][tmp.end];
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map[tmp.start][tmp.end] = -1;
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map[tmp.end][tmp.start] = -1;
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dijkstra(n);
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if (dis[n]>max)
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max = dis[n];
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map[tmp.start][tmp.end] = t;
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map[tmp.end][tmp.start] = t;
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}
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cout << max << endl;
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}
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return 0;
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}
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