HDU-2544-最短路

Posted 2021-01-07 angel-demon

• 迪杰斯特拉算法--O(nlogn)

  #include"iostream"
  #include"cstring"
  #include"cstdio"
  using namespace std;
  const int inf = 0x3f3f3f3f;
  typedef long long LL;
  int map[105][105];
  int ans[105], n, m;
  bool flag[105];
  void dij() {
      for(int i = 2; i <= n; i++)
      ans[i] = map[1][i];
      ans[1] = 0;
      memset(flag, true, sizeof(flag));
      flag[1] = false;
      for(int i = 2; i < n; i++) {
          int v, mn = inf;
          for(int j = 1; j <= n; j++)
          if(ans[j] < mn && flag[j]) {
              mn = ans[j];
              v = j;
          }
          for(int j = 1; j <= n; j++)
          if(ans[v] + map[v][j] < ans[j])
          ans[j] = ans[v] + map[v][j];
          flag[v] = false;
      }
  }
  int main() {
      int a, b, c;
      while(scanf("%d%d", &n, &m) && (n || m)) {
          memset(map, inf, sizeof(map));
          while(m--) {
              scanf("%d%d%d", &a, &b, &c);
              if(map[a][b] > c)
              map[a][b] = map[b][a] = c;
          }
          dij();
          printf("%d
  ", ans[n]);
      }
      return 0;
  }