算出来是389112

条件：

• 一共有9个点
• 至少经过4个点
• 每个点不能重复经过
• 直线上的中间点不能跳过

C++代码

/*
    0 1 2
    3 4 5
    6 7 8
*/
#include<cstdio>
#include<algorithm>

using namespace std;

bool check(int a, int b, int state) {
    if (a > b)  swap(a, b);
    if (a + 6 == b and !(state >> a + 3 & 1))  return false;
    if (a / 3 == b / 3 and a + 2 == b and !(state >> a + 1 & 1))  return false;
    if (a == 0 and b == 8 and !(state >> 4 & 1))  return false;
    if (a == 2 and b == 6 and !(state >> 4 & 1))  return false;
    return true;
}

int ones(int state) {
    int res = 0;
    while (state)  state -= state & -state, res ++;
    return res;
}

int res;
void dfs(int u, int state) {
    if (ones(state) >= 4)  res ++;
    for (int i = 0; i < 9; i ++) {
        if (!(state >> i & 1) and check(u, i, state))  dfs(i, state | (1 << i));
    }
}

int main() {
    for (int i = 0; i < 9; i ++)  dfs(i, 1 << i);
    printf("%d\n", res);
    return 0;
}