迷宫和树等的BFS及DFS

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1 DFS

#include <iostream>

#include<cstring>
#include<sstream>
using namespace std;

struct node
{
   int x, y;
};
char map[4][4] = { { '.', '.', '.', '.' }, { '.', '#', '#', '.' }, { '.', '#', '.', '.' }, { '.', '.', '.', '.' } };
int visit[4][4] = { 0 };
node star{ 0, 0 }, end{ 2, 2 };
int minstep = 600;
int dir[4][2] = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
int judge(int x, int y,int step)
{
   if ((2- x + 2 - y + step) > minstep)
       return 0;
   else
       return 1;
}
vector<node> minpath;
vector<node> path;
int step = -1;
void dfs(int x, int y,int step, vector<node> path)
{
   path.push_back(node{ x, y });
   visit[x][y] = 1;
   step++;
   if (x == 2 && y == 2)
   {
       if (step <= minstep)
       {
           minstep = step;
           minpath = path;
           for (int i = 0; i < minpath.size(); i++)
           {
               cout << minpath[i].x << " " << minpath[i].y << endl;
           }
           cout << "--------------------------"<< endl;
       }
       path.pop_back();
       visit[x][y] = 0;
       step--;

   }

   else
   {
       for (int i = 0; i < 4; i++)
       {
           int nx = x + dir[i][0];
           int ny = y + dir[i][1];
           if (judge(nx, ny, step) && nx >= 0 && nx < 4 && ny >= 0 && ny < 4 && map[nx][ny] == '.'&&visit[nx][ny] == 0)
           {
               dfs(nx, ny, step, path);
           }
       }
       path.pop_back();
       visit[x][y] = 0;
       step--;
   }

}

int main()
{
   dfs(0, 0,step,path);
   cout << minstep << endl;

   system("pause");
   return 0;
}

跟剑指offer25题一模一样，区别是树每条路径是向下所有孩子搜索，而迷宫是上下左右搜索，为了防止上下左右四个孩子回溯到本节点导致循环递归，设置visit变量。但是要记得本条路径搜索完毕之后visiti要复位，防止影响其他搜索路径的搜索！！

方法2 错误

#include<string>
using namespace std;
#include<iostream>
#include <vector>
#include<deque>
#include <list>
#include<queue>
#include<stack>
#include<algorithm>
#include <iomanip>
#include <functional>
#include <iostream>
#include<cstring>
#include<sstream>
using namespace std;

struct node
{
   int x, y;
};
char map[4][4] = { { '.', '.', '.', '.' }, { '.', '#', '#', '.' }, { '.', '#', '.', '.' }, { '.', '.', '.', '.' } };
int visit[4][4] = { 0 };
node star{ 0, 0 }, end{ 2, 2 };
int minstep = 600;
int dir[4][2] = { { -1, 0 }, { 1, 0 }, { 0, -1 }, { 0, 1 } };
int judge(int x, int y,int step)
{
   if ((2- x + 2 - y + step) > minstep)
       return 0;
   else
       return 1;
}
vector<node> minpath;
vector<node> path;
int step = 0;
void dfs(int x, int y,int step, vector<node> path)
{
   path.push_back(node{ x, y });
   visit[x][y] = 1;
   //step++;
   if (x == 2 && y == 2)
   {
       if (step <= minstep)
       {
           minstep = step;
           minpath = path;
           for (int i = 0; i < minpath.size(); i++)
           {
               cout << minpath[i].x << " " << minpath[i].y << endl;
           }
           cout << "--------------------------"<< endl;
       }
       path.pop_back();
       visit[x][y] = 0;
       //step--;

   }

   else
   {
       for (int i = 0; i < 4; i++)
       {
           int nx = x + dir[i][0];
           int ny = y + dir[i][1];
           if (judge(nx, ny, step) && nx >= 0 && nx < 4 && ny >= 0 && ny < 4 && map[nx][ny] == '.'&&visit[nx][ny] == 0)
           {
               int nstep = ++step;//ERROR!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!应该修改为int nstep=(step+1),并不能改变step的值，否则上下左右四个孩子的step起始值不一样了，影响其他三个孩子的最短路径判断！！！！
               dfs(nx, ny, nstep, path);

           }
       }
       path.pop_back();
       visit[x][y] = 0;
       //step--;
   }




}

int main()
{
   dfs(0, 0,step,path);
   cout << minstep << endl;

   system("pause");
   return 0;
}

2 BFS

#include <iostream>
#include<cstring>
#include<sstream>
using namespace std;

struct node
{
   int x, y, level;
};

int dir[4][2] = { { -1, 0 }, { 1, 0 }, {0,-1}, {0,1} };
int visit[10][10] = {0};
int sx = 0, sy = 0, ex = 2, ey = 2;
char map[4][4] = { { '.', '.', '.', '.' }, { '.', '#', '#', '.' }, { '.', '#', '.', '.' }, { '.', '.', '.', '.' } };

int bfs(char map[4][4])
{
   queue<node > q;
   node start{ 0, 0, 0 }, end{ 2, 2, 0 };
   q.push(start);
   visit[0][0] = 1;
   int m = 4, n = 4;
   while (!q.empty())
   {
       node now = q.front(),next;
       q.pop();
       for (int i = 0; i < 4; i++)
       {
           next.x = now.x + dir[i][0];
           next.y = now.y + dir[i][1];
           next.level = now.level + 1;
           if (next.x == ex&&next.y == ey)
               return next.level;
           if (next.x >= 0 && next.x < m && next.y >= 0 && next.y < n && visit[next.x][next.y] == 0 && map[next.x][next.y] == '.')
           {
               q.push(next);
               visit[next.x][next.y] = 1;
           }
       }

   }
   return 0;
}

int main()
{
   cout << bfs(map) << endl;
   system("pause");
   return 0;
}

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