题目链接:https://vjudge.net/contest/209862#problem/B
题目大意:
Trees on the level
Total Submission(s): 591 Accepted Submission(s): 200
This problem involves building and traversing binary trees.
Given a sequence of binary trees, you are to write a program that prints a level-order traversal of each tree. In this problem each node of a binary tree contains a positive integer and all binary trees have have fewer than 256 nodes.
In a level-order traversal of a tree, the data in all nodes at a given level are printed in left-to-right order and all nodes at level k are printed before all nodes at level k+1.
For example, a level order traversal of the tree
is: 5, 4, 8, 11, 13, 4, 7, 2, 1.
In this problem a binary tree is specified by a sequence of pairs (n,s) where n is the value at the node whose path from the root is given by the string s. A path is given be a sequence of L's and R's where L indicates a left branch and R indicates a right branch. In the tree diagrammed above, the node containing 13 is specified by (13,RL), and the node containing 2 is specified by (2,LLR). The root node is specified by (5,) where the empty string indicates the path from the root to itself. A binary tree is considered to be completely specified if every node on all root-to-node paths in the tree is given a value exactly once.
All nodes contain a positive integer. Every tree in the input will consist of at least one node and no more than 256 nodes. Input is terminated by end-of-file.
思路:先建树,判断其能否构成二叉树,若能,则用bfs层次遍历该二叉树
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<vector>
#include<queue>
using namespace std; const int maxn = + ; struct Node{
bool have_value;
int v;
Node* left, *right;
Node():have_value(false),left(NULL),right(NULL){}
}; Node* root; Node* newnode() { return new Node(); } bool failed;
void addnode(int v, char* s) {
int n = strlen(s);
Node* u = root;
for(int i = ; i < n; i++)
if(s[i] == 'L') {
if(u->left == NULL) u->left = newnode();
u = u->left;
} else if(s[i] == 'R') {
if(u->right == NULL) u->right = newnode();
u = u->right;
}
if(u->have_value) failed = true;
u->v = v;
u->have_value = true;
} void remove_tree(Node* u) {
if(u == NULL) return;
remove_tree(u->left);
remove_tree(u->right);
delete u;
} char s[maxn];
bool read_input() {
failed = false;
remove_tree(root);
root = newnode();
for(;;) {
if(scanf("%s", s) != ) return false;
if(!strcmp(s, "()")) break;
int v;
sscanf(&s[], "%d", &v);
addnode(v, strchr(s, ',')+);
}
return true;
} bool bfs(vector<int>& ans) {
queue<Node*> q;
ans.clear();
q.push(root);
while(!q.empty()) {
Node* u = q.front(); q.pop();
if(!u->have_value) return false;
ans.push_back(u->v);
if(u->left != NULL) q.push(u->left);
if(u->right != NULL) q.push(u->right);
}
return true;
} int main() {
vector<int> ans;
while(read_input()) {
if(!bfs(ans)) failed = ;
if(failed) printf("not complete\n");
else {
for(int i = ; i < ans.size(); i++) {
if(i != ) printf(" ");
printf("%d", ans[i]);
}
printf("\n");
}
}
return ;
}
2018-04-10