Depth-first search DFS, use recursion, which is equivalent to pre-order traversal
Breadth-first search BFS, use queue, access when push enters, mark
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
struct axis
{
axis() : x(-1), y(-1) {
}
axis(int x_, int y_) : x(x_), y(y_) {
}
int x;
int y;
};
void DFS(vector<vector<int>> &MAT, int i, int j);
void BFS(vector<vector<int>> &MAT, int i, int j);
int main()
{
vector<vector<int>> MAT{
{
1, 2, 3, 4, 5, 0, 0},
{
6, 7, 8, 9, 0, 0, 10},
{
0, 0, 11, 12, 13, 14, 0},
{
0, 15, 16, 0, 0, 17, 18},
{
19, 20, 0, 0, 0, 24, 0}};
DFS(MAT, 2, 3);
BFS(MAT, 2, 3);
return 0;
}
//深度优先,用递归,相当于先序遍历
void DFS(vector<vector<int>> &MAT, int i, int j)
{
int row = MAT.size();
int col = MAT[0].size();
cout << i << " " << j << " " << MAT[i][j] << endl;
MAT[i][j] = -1;
if (i - 1 >= 0 && j >= 0 && i - 1 < row && j < col && MAT[i - 1][j] != -1)
DFS(MAT, i - 1, j);
if (i + 1 >= 0 && j >= 0 && i + 1 < row && j < col && MAT[i + 1][j] != -1)
DFS(MAT, i + 1, j);
if (i >= 0 && j - 1 >= 0 && i < row && j - 1 < col && MAT[i][j - 1] != -1)
DFS(MAT, i, j - 1);
if (i >= 0 && j + 1 >= 0 && i < row && j + 1 < col && MAT[i][j + 1] != -1)
DFS(MAT, i, j + 1);
}
//广度优先搜索, 用队列, push进去的时候访问,标记
void BFS(vector<vector<int>> &MAT, int i, int j)
{
int row = MAT.size();
int col = MAT[0].size();
queue<axis> QUEUE;
QUEUE.push(axis(i, j));
cout << i << " " << j << " " << MAT[i][j] << endl;
MAT[i][j] = -1;
axis front;
int x, y;
while (!QUEUE.empty())
{
front = QUEUE.front();
QUEUE.pop();
x = front.x;
y = front.y;
if (x - 1 >= 0 && x - i < row && MAT[x - 1][y] != -1)
{
QUEUE.push(axis(x - 1, y));
cout << x - 1 << " " << y << " " << MAT[x - 1][y] << endl;
MAT[x - 1][y] = -1;
}
if (x + 1 >= 0 && x + 1 < row && MAT[x + 1][y] != -1)
{
QUEUE.push(axis(x + 1, y));
cout << x + 1 << " " << y << " " << MAT[x + 1][y] << endl;
MAT[x + 1][y] = -1;
}
if (y - 1 >= 0 && y - 1 < col && MAT[x][y - 1] != -1)
{
QUEUE.push(axis(x, y - 1));
cout << x << " " << y - 1 << " " << MAT[x][y - 1] << endl;
MAT[x][y - 1] = -1;
}
if (y + 1 >= 0 && y + 1 < col && MAT[x][y + 1] != -1)
{
QUEUE.push(axis(x, y + 1));
cout << x << " " << y + 1 << " " << MAT[x][y + 1] << endl;
MAT[x][y + 1] = -1;
}
}
}