pta 编程题7 List Leaves
其它pta数据结构编程题请参见：pta
这次的编程作业要求从上到下，从左到右输出一棵树的叶子节点，即树的层序遍历，用队列的方式来实现。
注意enqueue和dequeue函数参数为Queue &q，而不是Queue q，即用引用的方式才能改变实参的值。
1 #include <iostream> 2 using namespace std; 3 4 struct Node 5 { 6 int left; 7 int right; 8 }; 9 10 struct Queue 11 { 12 int data[10]; 13 int first = -1; 14 int end = -1; 15 int maxSize = 10; 16 }; 17 18 int buildTree(Node tree[]); 19 void enqueue(Queue &q, int i); 20 int dequeue(Queue &q); 21 bool empty(Queue q); 22 23 int main() 24 { 25 Node tree1[10]; 26 int root = buildTree(tree1); 27 Queue q, leaves; 28 int t, cnt = 0; 29 enqueue(q, root); 30 while (!empty(q)) 31 { 32 t = dequeue(q); 33 if (tree1[t].left == -1 && tree1[t].right == -1) 34 enqueue(leaves, t); 35 if (tree1[t].left != -1) enqueue(q, tree1[t].left); 36 if (tree1[t].right != -1) enqueue(q, tree1[t].right); 37 } 38 while (!empty(leaves)) 39 { 40 if (cnt > 0) cout << " "; 41 cout << dequeue(leaves); 42 cnt++; 43 } 44 return 0; 45 } 46 47 int buildTree(Node tree[]) 48 { 49 int num, i, root = -1; 50 char l, r; 51 cin >> num; 52 int judgeRoot[10] = {}; 53 for (i = 0; i < num; i++) 54 { 55 cin >> l >> r; 56 if (l != '-') 57 { 58 tree[i].left = l - '0'; 59 judgeRoot[l - '0'] = 1; 60 } 61 else tree[i].left = -1; 62 if (r != '-') 63 { 64 tree[i].right = r - '0'; 65 judgeRoot[r - '0'] = 1; 66 } 67 else tree[i].right = -1; 68 } 69 for (i = 0; i < num; i++) 70 { 71 if (judgeRoot[i] == 0) root = i; 72 } 73 return root; 74 } 75 76 void enqueue(Queue &q, int i) 77 { 78 q.end = (q.end + 1) % 10; 79 q.data[q.end] = i; 80 } 81 82 int dequeue(Queue &q) 83 { 84 q.first = (q.first + 1) % 10; 85 return q.data[q.first]; 86 } 87 88 bool empty(Queue q) 89 { 90 return q.end == q.first; 91 }
