PAT 1127—— ZigZagging on a Tree(中序後序求解樹)
阿新 • • 發佈:2018-11-09
#include <queue>
#include <iostream>
#include <cstdio>
using namespace std;
vector<int> inOrder, postOrder;
int N;
struct TreeNode
{
int value;
TreeNode *left, *right;
TreeNode(const int x) : value(x), left(nullptr), right(nullptr) {}
};
void makeTree(TreeNode *&rootNode, int inBegin, int inEnd, int postBegin, int postEnd)
{
if (inBegin > inEnd || inBegin < 0 || postBegin < 0 || inEnd > N - 1 || postEnd > N - 1)return;
int rootIndex = inBegin;
while (rootIndex <= inEnd && inOrder[rootIndex] != postOrder[postEnd])rootIndex++;
rootNode = new TreeNode(inOrder[rootIndex]);
int new_inBegin = inBegin;
int new_inEnd = rootIndex - 1;
int new_postBegin = postBegin;
int new_postEnd = postBegin + (new_inEnd - new_inBegin);
makeTree(rootNode->left, new_inBegin, new_inEnd, new_postBegin, new_postEnd);
new_inBegin = rootIndex + 1 ;
new_inEnd = inEnd;
new_postBegin = postBegin + (rootIndex - inBegin);//這一塊一定要注意
new_postEnd = postEnd - 1;//這一塊一定要注意
makeTree(rootNode->right, new_inBegin, new_inEnd, new_postBegin, new_postEnd);
}
int main()
{
scanf_s("%d", &N);
inOrder.reserve(N + 2);
inOrder.resize(N + 2);
postOrder.reserve(N + 2);
postOrder.resize(N + 2);
for (int i = 0; i < N; ++i)
{
scanf_s("%d", &inOrder[i]);
}
for (int i = 0; i < N; ++i)
{
scanf_s("%d", &postOrder[i]);
}
TreeNode *root = nullptr;
makeTree(root, 0, N - 1, 0, N - 1);
TreeNode *last = nullptr, *newLast = nullptr;
vector<vector<int>>result;
vector<int>temp;
queue<TreeNode*> Q;
Q.push(root);
last = newLast = root;
while (!Q.empty())
{
TreeNode *node = Q.front();
Q.pop();
temp.push_back(node->value);
if (node->left != nullptr)
{
Q.push(node->left);
newLast = node->left;
}
if (node->right != nullptr)
{
Q.push(node->right);
newLast = node->right;
}
if (last->left == newLast || last->right == newLast)
{
last = newLast;
result.push_back(temp);
temp.clear();
}
}
if (!temp.empty())result.push_back(temp);
int resultSize = result.size();
printf("%d", result[0][0]);
for (int i = 1; i < resultSize; i++) {
if (i % 2 == 1) {
for (int j = 0; j < result[i].size(); j++)
printf(" %d", result[i][j]);
}
else {
for (int j = result[i].size() - 1; j >= 0; j--)
printf(" %d", result[i][j]);
}
}
}