DFS搜索联通块

对一个3*4方格进行深度优先搜索联通块，有一个缺点是有一种联通快搜索不到。

#include <iostream>
#include <cmath>

using namespace std;

int m = 3, n = 4, sum = 0;
int pic[3][4];
bool visit[3][4] = { false };

void dfs(int i, int j, int cnt)
{
if (i < 0 || i >= m || j < 0 || j >= n)
    {
return;
    }
if (visit[i][j] == true)
    {

return;
    }
// pic[i][j] = cnt;
    visit[i][j] = true;
if (cnt == 5)
    {
        sum++;
return;
    }
for (int i2 = -1; i2 <= 1; i2++)
    {
for (int j2 = -1; j2 <= 1; j2++)
        {
int abs_ij = abs(i2) + abs(j2);
if (abs_ij != 2 && abs_ij != 0 && !visit[i+i2][j+j2])
            {
// visit[i2][j2] = true;
                dfs(i + i2, j + j2, cnt + 1);
                visit[i+i2][j+j2] = false;
            }
        }
    }
}

int main()
{
for (int i = 0; i < m; i++)
    {
for (int j = 0; j < n; j++)
        {
            pic[i][j] = 0;
        }
    }
for (int i = 0; i < m; i++)
    {
for (int j = 0; j < n; j++)
        {
int cnt = 0;
            dfs(i, j, cnt + 1);
        }
    }

cout << "sum: " << sum << endl;
return 0;
}