POJ3268之最短路

来源：互联网发布：网络黄金合法吗编辑：程序博客网时间：2024/05/18 18:42

#include <iostream>  #define INF 0x1f1f1f1f  #define MAX_SIZE 1005  using namespace std;    int map[MAX_SIZE][MAX_SIZE];  int dis[MAX_SIZE];  bool mark[MAX_SIZE];    void init(int n)  {      for(int i = 1; i <= n; ++i)      {          for(int j = 1; j <= n; ++j)              map[i][j] = INF;          map[i][i] = 0;      }  }    void dijkstar(int start, int n)  {      for(int i = 1; i <= n; ++i)      {          dis[i] = map[start][i];          mark[i] = false;      }        dis[start] = 0;      mark[start] = true;        int mindis, tag;        while(1)      {          mindis = INF;          for(int i = 1; i <= n; ++i)          {              if(!mark[i] && mindis > dis[i])              {                  mindis = dis[i];                  tag = i;              }          }            mark[tag] = true;            if(mindis == INF)  break;            for(int i = 1; i <= n; ++i)          {              if(!mark[i] && dis[i] > dis[tag] + map[tag][i])                  dis[i] = dis[tag] + map[tag][i];          }      }  }    int main()  {      ///需要看看以前的代码，所以还是不够熟，加油！！      int n, m, end;      while(cin >> n >> m >> end)      {          init(n);            int x, y, w;          while(m--)          {              cin >> x >> y >> w;              if(map[x][y] > w)                  map[x][y] = w;          }            int sum2[MAX_SIZE];          dijkstar(end, n);          for(int i = 1; i <= n; ++i)          {              sum2[i] = dis[i];          }            int temp;          for(int i = 1; i <= n; ++i)          {              for(int j = i + 1; j <= n; ++j)              {                      temp = map[i][j];                      map[i][j] = map[j][i];                      map[j][i] = temp;              }          }            int sum1[MAX_SIZE];          dijkstar(end, n);          for(int i = 1; i <= n; ++i)          {              sum1[i] = dis[i];          }            int max = -1;          for(int i = 1; i <= n ; ++i)          {              max = (max > sum1[i] + sum2[i]) ? max : sum1[i] + sum2[i];          }          cout << max << endl;        }        return 0;  }

今天把以前有用的东西整理一下

这个是自己第一次写的，比较好理解，但优化不够

#include <iostream>  #define INF 0x1f1f1f1f  #define N 1005  using namespace std;  int map1[N][N], map2[N][N];//建两个图，一个是另一个的转置  int dis1[N], dis2[N];  bool mark1[N], mark2[N];  int n, m, x;    void init()  {      int i, j;      for(i = 1; i <= n; ++i)          {            for(j = 1; j <= n; ++j)            {                map1[i][j] = INF;                map2[i][j] = INF;            }            map1[i][i] = 0;            map2[i][i] = 0;          }    }    void dijFirst(int start, int n)  {      int i, j, mindis, k;      for(i = 1; i <= n; ++i)      {          dis1[i] = map1[start][i];          mark1[i] = false;      }      dis1[start] = 0;      mark1[start] = true;        while(1)      {          mindis = INF;          for(j = 1; j <= n; ++j)          {              if(!mark1[j] && mindis > dis1[j])              {                  mindis = dis1[j];                  k = j;              }          }          mark1[k] = true;          if(mindis == INF)  break;            for(j = 1; j <= n; ++j)          {              if(!mark1[j] && dis1[j] > dis1[k] + map1[k][j])                  dis1[j] = dis1[k] + map1[k][j];          }      }  }    void dijSecond(int start, int n)  {      int i, j, mindis, k;      for(i = 1; i <= n; ++i)      {          dis2[i] = map2[start][i];          mark2[i] = false;      }      dis2[start] = 0;      mark2[start] = true;        while(1)      {          mindis = INF;          for(j = 1; j <= n; ++j)          {              if(!mark2[j] && mindis > dis2[j])              {                  mindis = dis2[j];                  k = j;              }          }          mark2[k] = true;          if(mindis == INF)  break;            for(j = 1; j <= n; ++j)          {              if(!mark2[j] && dis2[j] > dis2[k] + map2[k][j])                  dis2[j] = dis2[k] + map2[k][j];          }      }  }    int main()  {      int i, j;      while(cin >> n >> m >> x)      {          init();          for(i = 1; i <= m; ++i)          {              int u, v ,w;              cin >> u >> v >> w;              map2[u][v] = w;          }            int max;          max = 0;          dijSecond(x, n);  ///最关键的地方，将矩阵转置以后，从终节点出发到其他节点的距离，就是反向走有向图          for(i = 1; i <= n; ++i)          {              for(j = 1; j <= n; ++j)              {                  map1[i][j] = map2[j][i];              }          }            dijFirst(x, n);          for(i = 1; i <= n; ++i)          {              max = (dis1[i] + dis2[i] > max) ? (dis1[i] + dis2[i]) : max;          }          cout << max << endl;          }      //cout << "Hello world!" << endl;      return 0;  }

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