03-树2 List Leaves (25分)
Given a tree, you are supposed to list all the leaves in the order of top down, and left to right.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer NN (\le 10≤10) which is the total number of nodes in the tree – and hence the nodes are numbered from 0 to N-1N−1. Then NN lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a “-” will be put at the position. Any pair of children are separated by a space.
Output Specification:
For each test case, print in one line all the leaves’ indices in the order of top down, and left to right. There must be exactly one space between any adjacent numbers, and no extra space at the end of the line.
Sample Input:
8 1 - - - 0 - 2 7 - - - - 5 - 4 6 Sample Output:
4 1 5
AC代码如下：
#include <iostream>
#include <vector>
#include <queue>
using namespace std;
struct Node{
int data;
int left;
int right;
};
//建树函数，返回根节点
int BuildTree(vector<struct Node> &Tree,int N){
int root = -1;
char left,right;
vector<int> check(N,0);
for ( int i = 0 ; i < N ; i++){
cin>>left>>right;
Tree[i].data = i;
//判断左子树是否为空，不为空则把ckeck数组相应位置1,否则置-1
if ( left != '-'){
Tree[i].left = (int)(left-'0');
check[Tree[i].left] = 1;
}else{
Tree[i].left = -1;
}
//判断右子树是否为空，不为空则把ckeck数组相应位置1,否则置-1
if ( right != '-'){
Tree[i].right = (int)(right-'0');
check[Tree[i].right] = 1;
}else{
Tree[i].right = -1;
}
}
//寻找根节点的索引
for ( int i = 0 ; i < N ; i++){
if ( check[i] == 0){
root = i;
break;
}
}
return root;
}
//寻找叶子节点函数
vector<int> Find_Leaves(vector<struct Node> &Tree,int root)
{
vector<int> leaves;
queue<struct Node> que;
struct Node treenode;
if ( root == -1){
return {};
}else{
que.push(Tree[root]);
while(!que.empty()){
treenode = que.front();
que.pop();
if ( treenode.left == -1 && treenode.right == -1){
leaves.push_back(treenode.data);
}
if ( treenode.left != -1){
que.push(Tree[treenode.left]);
}
if ( treenode.right != -1){
que.push(Tree[treenode.right]);
}
}
}
return leaves;
}
void Print(vector<int> & leaves)
{
cout<<leaves[0];
for ( int i = 1 ; i < leaves.size() ; i++){
cout<<" "<<leaves[i];
}
}
int main()
{
int N;//树节点的个数
cin>>N;
vector<struct Node> Tree(N); //存储树结点的数组
//完成建树过程，返回根节点索引
int root = BuildTree(Tree,N);
//寻找叶子结点数组
vector<int> leaves = Find_Leaves(Tree,root);
//打印所有叶子结点
Print(leaves);
return 0;
}