#include <stdio.h>
#define V 100
int n, m, ans, e[V][V], visited[V];
void dfs(int x, int len)
{
int i;
visited[x] = 1;
if (len > ans)
ans = len;
for (i = 1; i <= n; i++)
if ((visited[i] == 0) && (e[x][i] != -1))
dfs(i, len + e[x][i]);  
visited[x] = 0;
}
int main()
{
int i, j, a, b, c;
scanf("%d%d", &n, &m);
for (i = 1; i <= n; i++)
for (j = 1; j <= n; j++)
e[i][j] = -1;
for (i = 1; i <= m; i++) {
scanf("%d%d%d", &a, &b, &c);
e[a][b] = c;
e[b][a] = c;
}
for (i = 1; i <= n; i++)
visited[i] = 0;
ans = 0;
for (i = 1; i <= n; i++)
dfs(i, 0);
printf("%d\n", ans);
return 0;
}
输入：
4 6
1 2 10
2 3 20
3 4 30
4 1 40
1 3 50
2 4 60
输出：____150_____
程序没有问题，可是我在主函数第四次调用dfs时就出不来这个答案，请高手指点。

#include <stdio.h>
#define V 100
int n, m, ans, e[V][V], visited[V];
void dfs(int x, int len)
{
       int i;
       visited[x] = 1;
        if (len > ans)
           ans = len;
           for (i = 1; i <= n; i++)
              if ((visited[i] == 0) && (e[x][i] != -1))
                  dfs(i, len + e[x][i]);  
              visited[x] = 0;
     }
  int main()
    {
           int i, j, a, b, c;
           scanf("%d%d", &n, &m);
           for (i = 1; i <= n; i++)
              for (j = 1; j <= n; j++)
                e[i][j] = -1;
          for (i = 1; i <= m; i++) {
              scanf("%d%d%d", &a, &b, &c);
              e[a][b] = c;
              e[b][a] = c;
           }
  for (i = 1; i <= n; i++)
        visited[i] = 0;
        ans = 0;
  for (i = 1; i <= n; i++)
       dfs(i, 0);
       printf("%d\n", ans);
  return 0;
}
这样可以了吗？？

那你懂这个程序吗？？？？高手？？

能解题就谢了，新手才需要帮忙的啊？？

我也知道在遍历无向图，也知道答案，我需要知道的是：这个程序是怎么实现这个功能的？程序是怎么运行到结果的？