sicily：1155.Can I Post the letter

深度优先搜索的核心是确定下一层节点的选择。

<span style="font-size:14px;">#include <iostream>#include <queue>using namespace std;const int MAX_SIZE = 201;int map[MAX_SIZE][MAX_SIZE];bool visited[MAX_SIZE];int n, m;bool ans;void init() {ans = false;for (int i = 0; i < n; i++) {for (int j = 0; j < n; j++)map[i][j] = -1;map[i][i] = 0;visited[i] = false;}}void bfs(int s) {visited[s] = true;queue<int> q;q.push(s);while (!q.empty()) {int u = q.front();for (int i = 0; i < n; i++) {if (map[u][i] > 0 && !visited[i]) {if (i == n - 1) {ans = true;break;}visited[i] = true;q.push(i);}}q.pop();}}int main() {while (cin >> n && n) {init();cin >> m;int u, v;for (int i = 0; i < m; i++) {cin >> u >> v;map[u][v] = 1;}bfs(0);if (ans) cout << "I can post the letter\n";else cout << "I can't post the letter\n";}return 0;}</span>