uva122-树的层次遍历

思路：建树，遍历树。

代码：

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 1000 + 20;
char s[maxn];
bool failed;
vector<int> ans;
struct Node {
bool hv;
int v;
Node *left, *right;
Node():hv(false),left(NULL), right(NULL) { }
};
Node* root;
Node* newnode() { return new Node();}
void addnode(int v, char* s)
{
int len = strlen(s);
Node *u = root;
for (int i=0; i<len; 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->hv) failed = true; // 表示已经赋过值了
u->v = v;
u->hv = true;
}
bool read_input()
{
failed = false;
root = newnode();
while (1) {
if (scanf("%s", s) != 1) return false;
if (!strcmp(s, "()")) break;
int v;
sscanf(&s[1], "%d", &v);
addnode(v, strchr(s, ',')+1);
}
return true;
}

bool bfs(vector<int>& ans)
{
queue<Node*> q;
ans.clear();
q.push(root); // 初始一个根节点
while (!q.empty()) {
Node* u = q.front(); q.pop();
if (!u->hv) return false; //有节点未被赋值
ans.push_back(u->v); // 增加到输出序列尾部
if (u->left != NULL) q.push(u->left);
if (u->right != NULL) q.push(u->right);
}
return true;
}

int main()
{
int n;
while (read_input()) //输入
{
bfs(ans); //bfs遍历
if (failed || !bfs(ans)) puts("not complete");
else {
for (int i=0; i<ans.size(); i++) {
if (i) printf(" "); printf("%d", ans[i]);
}
puts("");
}
}
return 0;
}