就是树的层次遍历，BFS算法。要判断给出的数据能不能构成一颗正确的树（不能缺漏或重叠）。
要写一个树的结构。可以有两种写法：
①：用纯指针，结构体里要有左右结点指针，结点存储的值，还有结点相关的必要信息。要注意使用后要释放结点的内存，用指针访问比数组更快。
②：用数组来表示，比较方便。将左右结点和值信息等等全都单独建一个数组。数组中某个序号代表某一结点 比如left[5]代表结点5的left子树的序号的值。不用管理内存。
下边分别是用指针和数组的方法
1 #include<iostream> 2 #include<string> 3 #include<queue> 4 using namespace std; 5 bool complete = true; 6 7 8 struct node { 9 int val; bool has_valuaed; node *left; node *right; 10 node() :val(-1), has_valuaed(false), left(NULL), right(NULL) {} 11 }; 12 node * newtree() { return new node(); } 13 node *t = newtree(); 14 15 bool addnode(int v, string S) 16 { 17 node *p = t; 18 while (S.size()) 19 { 20 if (S[0] == 'L') 21 { 22 if (p->left == NULL) p->left = new node(); 23 p = p->left; 24 } 25 if (S[0] == 'R') 26 { 27 if (p->right == NULL) p->right = new node(); 28 p = p->right; 29 } 30 if (S[0] == ')') 31 { 32 if (p->val != -1) { complete = false; return false; } 33 p->val = v; p->has_valuaed = true; 34 } 35 S.erase(S.begin()); 36 } 37 return true; 38 } 39 void remove_tree(node* t) 40 { 41 if (t == NULL) return; 42 remove_tree(t->left); 43 remove_tree(t->right); 44 delete t; 45 } 46 47 48 void bfs(queue<int>&Q) 49 { 50 queue<node*> output; 51 output.push(t); 52 while (!output.empty()) 53 { 54 node *f = output.front(); 55 if (f->val < 0) { 56 complete = false; break; 57 } 58 else Q.push(f->val); 59 if (f->left != NULL) output.push(f->left); 60 if (f->right != NULL) output.push(f->right); 61 output.pop(); 62 } 63 } 64 65 66 int main() 67 { 68 string S; 69 while (cin >> S) 70 { 71 72 if (S == "()") 73 { 74 queue<int> outputval; 75 bfs(outputval); 76 //输出 77 if (complete) 78 { 79 while(outputval.size()) 80 { 81 cout << outputval.front(); 82 if (outputval.size() != 1)cout << " "; 83 outputval.pop(); 84 } 85 cout << endl; 86 } 87 else cout << "not complete" << endl; 88 //初始化 89 remove_tree(t); 90 t = newtree(); complete = true; 91 } 92 else 93 {//输入 94 string::size_type idx; 95 string Temp = S.substr(1, S.find(',') - 1); 96 int v = stoi(Temp, &idx); 97 S = S.substr(S.find(',') + 1, S.size() - 1); 98 addnode(v, S); 99 } 100 } 101 return 0; 102 }
1 #include<iostream> 2 #include<string> 3 #include<queue> 4 #define maxl 250 5 #define mms(a,b) memset(a,b,sizeof(a)) 6 using namespace std; 7 bool complete = true; 8 9 int left_[maxl], right_[maxl], val[maxl], have_value[maxl], cnt = 0; 10 11 void newtree() { val[0]=have_value[0] = right_[0] = left_[0] = 0; } 12 int newnode() { 13 int n = ++cnt; val[n]=have_value[n] = right_[n] = left_[n] = 0; 14 return n; 15 } 16 bool addnode(int v, string S) 17 { 18 int p = 0; 19 while (S.size()) 20 { 21 if (S[0] == 'L') 22 { 23 if (left_[p] <1) left_[p] = newnode(); 24 p = left_[p]; 25 } 26 if (S[0] == 'R') 27 { 28 if (right_[p] <1) right_[p] = newnode(); 29 p = right_[p]; 30 } 31 if (S[0] == ')') 32 { 33 if (have_value[p] == 1) { complete = false; return false; } 34 val[p] = v; have_value[p]++; 35 } 36 S.erase(S.begin()); 37 } 38 return true; 39 } 40 41 void bfs(queue<int>&Q) 42 { 43 queue<int> output; 44 output.push(0); 45 while (!output.empty()) 46 { 47 int f = output.front(); 48 if (have_value[f]!=1) { 49 complete = false; break; 50 } 51 else Q.push(val[f]); 52 if (left_[f] > 0) output.push(left_[f]); 53 if (right_[f] > 0) output.push(right_[f]); 54 output.pop(); 55 } 56 } 57 58 void remove_tree() 59 { 60 mms(left_, -1); mms(right_, -1); mms(have_value, -1); mms(val, -1); 61 } 62 63 int main() 64 { 65 string S; remove_tree(); newtree(); 66 while (cin >> S) 67 { 68 if (S == "()") 69 { 70 queue<int> outputval; 71 bfs(outputval); 72 //输出 73 if (complete) 74 { 75 while (outputval.size()) 76 { 77 cout << outputval.front(); 78 if (outputval.size() != 1)cout << " "; 79 outputval.pop(); 80 } 81 cout << endl; 82 } 83 else cout << "not complete" << endl; 84 //初始化 85 remove_tree(); 86 newtree(); complete = true; 87 } 88 else 89 {//输入 90 string::size_type idx; 91 string Temp = S.substr(1, S.find(',') - 1); 92 int v = stoi(Temp, &idx); 93 S = S.substr(S.find(',') + 1, S.size() - 1); 94 addnode(v, S); 95 } 96 } 97 return 0; 98 }