/**************************************************
有向图的非递归遍历， 程序假如图的强联通的
如果不是强联通简单修改即可。
*************************************************/
#include <iostream>
#include <cstdio>
using namespace std;
const int maxsize = 100;
typedef struct sqstack {
    int data[maxsize];
    int top;
}sqstack;
void InitStack(sqstack &s) {
    s.top = -1;
}
bool StackEmpty(sqstack s) {
    if(s.top == -1) return true;
    else return false;
}
bool StackFull(sqstack s) {
    if(s.top == maxsize-1) return true;
    else return false;
}
bool Push(sqstack &s, int x) {
    if(s.top == maxsize-1) return false;
    s.data[++s.top] = x;
    return true;
}
bool Pop(sqstack &s, int &x) {
    if(s.top == -1) return false;
    x = s.data[s.top--];
    return true;
}
bool GetTop(sqstack s, int &x) {
    if(s.top == -1) return false;
    x = s.data[s.top];
    return true;
}

int mat[maxsize][maxsize];
int n, m; // 图的顶点和边。图的顶点标号从1到n

void DFS(int v) {
    int tmp;
    bool vis[maxsize];
    sqstack s;
    InitStack(s);
    memset(vis, false, sizeof(vis));
    Push(s, v);
    vis[v] = true;
    while(!StackEmpty(s)) {
        Pop(s, tmp);
        printf("%d  ", tmp);
        for(int i = 1; i <= n; i++) {
            if(mat[tmp][i]==1 && !vis[i]) {
                Push(s, i);
                vis[i] = true; // marked.
            }
        }

    }
}

void input_map() {
    int from, to;
    memset(mat, 0, sizeof(mat));
    printf("请输入总的顶点数和边数：\n");
    cin >> n >> m;
    printf("输入每一条边的起点和终点\n");
    for(int i = 0; i < m; i++) {
        cin >> from >> to;
        mat[from][to] = 1;
    }
}
int main() {
    input_map();
    printf("please input the start point\n");
    int start;
    cin >> start;
    DFS(start);
    return 0;
}
/**
Test:
6 8
1 2
1 4
2 3
2 4
3 6
4 5
5 3
6 5
**/