前序/中序--->后序

参考：http://www.cnblogs.com/rain-lei/p/3576796.html

！！由前序和后序序列无法确定二叉树

preOrder 5 3 2 4 8 6 9   midOrder 2 3 4 5 6 8 9  postOrder 2 4 3 6 9 8 5

#include <iostream>
using namespace std;

const int maxn = ;

typedef struct Node
{
    int key;
    struct Node *left;
    struct Node *right;
}treeNode;

int preOrder[maxn];
int midOrder[maxn];

// 由中序和后序序列创建树
treeNode *createTree(int preLeft, int preRight, int midLeft, int midRight)
{
    if (preRight - preLeft < ) return NULL;
    treeNode *root = new treeNode;
    root->key = preOrder[preLeft];
    if (preRight == preLeft)
    {
        root->left = NULL;
        root->right = NULL;
    }

    int index;
    for (index = midLeft; index <= midRight; ++index)
    {
        if (midOrder[index] == preOrder[preLeft]) break;
    }
    root->left = createTree(preLeft + , preLeft + (index - midLeft), midLeft, index - );
    root->right = createTree(preLeft + (index - midLeft) + , preRight, index + , midRight);
    return root;
}

void postOrder(treeNode *root)
{
    if (root != NULL)
    {
        postOrder(root->left);
        postOrder(root->right);
        cout << root->key << " ";
    }
}

int main()
{
    int n;
    cout << "Input the number of Node: " << endl;
    cin >> n;
    cout << "The preOrder: " << endl;
    for (int i = ; i < n; ++i)
        cin >> preOrder[i];
    cout << "The midOrder: " << endl;
    for (int i = ; i < n; ++i)
        cin >> midOrder[i];
    treeNode *root = createTree(, n - , , n - );
    cout << "The postOrder: " << endl;
    postOrder(root);
    cout << endl;
    system("pause");
    return ;

}