算法之路（二）

上一篇寫了DFS的遞歸方式實現，這次寫一下非遞歸實現。

原理其實非常簡單：我用棧去實現的，棧實現的基本思路是將一個節點所有未被訪問的“鄰居”（即一層層鄰居節點）壓入棧中“待用”，然後圍繞頂部節點猛攻，每個節點訪問 後被彈出。下面是實現的代碼，僅供參考~

#include <iostream>
#include <stack>
using namespace std;

#define MaxNode 20
#define MAX 20000

int map[MaxNode + 1][MaxNode + 1];

void dfs_stack(int start, int n)
{
int visited[MaxNode], s_top;
for (int i = 0; i <= MaxNode; i++)
{
visited[i] = 0;
}
visited[start] = 1;

stack<int> s;
cout << start << " ";

for (int i = 1; i <=n; i++)
{
if (map[i][start] == 1 && !visited[i])
{
visited[i] = 1;
s.push(i);
}
}

while (!s.empty())
{
s_top = s.top();
visited[s_top] = 1;
cout << s_top << " ";
s.pop();
for (int i = 0; i <= n; i++)
{
if (map[i][s_top] == 1 && !visited[i])
{
visited[i] = 1;
s.push(i);
}
}
}
}

int main(int argc, const char* argv[])
{
int num_edge, num_node;
int x, y;
cout << "Input number of nodes and edges" << endl;
cin >> num_node >> num_edge;


for (int i = 0; i < num_node; i++)
{
for (int j = 0; j < num_node; j++)
{
map[i][j] = 0;
}
}
for (int i = 1; i <= num_edge; i++)
{
cin >> x >> y;
map[x][y] = map[y][x] = 1;
  }

dfs_stack(0, num_node);

return 0;
}