[jobdu]树的子结构

判断一棵树B是否是A的子树，对A做DFS，然后不断判断是否和B相同。

其实也可以不对A做DFS，直接遍历A中的每个节点和B做树的比较就行了。

#include <iostream>

#include <vector>

using namespace std;

  

bool sameTree(int a, int b, vector<vector<int> > &treeA, vector<vector<int> > &treeB, vector<int> &valA, vector<int> &valB) {

    if (valA[a] != valB[b]) return false;

    if (treeB[b].size() == 0) return true;

    if (treeA[a].size() != treeB[b].size()) return false;

    for (int i = 0; i < treeA[a].size(); i++) {

        if (!sameTree(treeA[a][i], treeB[b][i], treeA, treeB, valA, valB))

            return false;

    }

    return true;

}

  

bool subTree(vector<vector<int> > &treeA, vector<vector<int> > &treeB, vector<int> &valA, vector<int> &valB, int root) {

    if (sameTree(root, 1, treeA, treeB, valA, valB)) {

        return true;

    }

    for (int i = 0; i < treeA[root].size(); i++) {

        if (subTree(treeA, treeB, valA, valB, treeA[root][i])) {

            return true;

        }

    }

    return false;

}

  

int main() {

    int n, m;

    while (cin >> n >> m)

    {

        vector<vector<int> > treeA(n+1);

        vector<vector<int> > treeB(m+1);

        vector<int> valA(n+1);

        vector<int> valB(m+1);

        for (int i = 1; i <= n; i++) {

            int tmp;

            cin >> tmp;

            valA[i] = tmp;

        }

        for (int i = 1; i <= n; i++) {

            int cnt;

            cin >> cnt;

            while (cnt--) {

                int x;

                cin >> x;

                treeA[i].push_back(x);

            }

        }

        for (int i = 1; i <= m; i++) {

            int tmp;

            cin >> tmp;

            valB[i] = tmp;

        }

        for (int i = 1; i <= m; i++) {

            int cnt;

            cin >> cnt;

            while (cnt--) {

                int x;

                cin >> x;

                treeB[i].push_back(x);

            }

        }

  

        if (m == 0 || n == 0) {

            cout << "NO" << endl;

            continue;

        }

        if (subTree(treeA, treeB, valA, valB, 1)) {

            cout << "YES" << endl;

        }

        else {

            cout << "NO" << endl;

        }

    }

}