HDU 1710

http://acm.hdu.edu.cn/showproblem.php?pid=1710

题意：给二叉树的先序遍历和中序遍历，确定后序遍历

解法：复习专业课找的一题，根据先序遍历和中序遍历建树，再对树做后序遍历

#include <iostream>
#include <cstdio>

using namespace std;

struct Tree {
    Tree *lc, *rc;
    int data;
};

Tree *Create(int *preorder, int *inorder, int n) {
    for(int i = 0; i < n; i++) {
        if(preorder[0] == inorder[i]) {
            Tree *node = (Tree*)malloc(sizeof(Tree));
            node -> data = preorder[0];
            node -> lc = Create(preorder+1, inorder, i);
            node -> rc = Create(preorder+i+1, inorder+i+1, n-i-1);
            return node;
        }
    }
    return NULL;
}

int rt;

void PostOrder(Tree *root) {
    if(root != NULL) {
        PostOrder(root -> lc);
        PostOrder(root -> rc);
        if(root -> data == rt)
            printf("%d\n", root->data);
        else
            printf("%d ", root->data);
    }
}

Tree *root;
int preorder[1005], inorder[1005]; 

int main() {
    int n;
    while(~scanf("%d", &n)) {
        for(int i = 0; i < n; i++)
            scanf("%d", &preorder[i]);
        for(int i = 0; i < n; i++)
            scanf("%d", &inorder[i]);
        root = NULL;
        rt = preorder[0];
        root = Create(preorder, inorder, n);
        PostOrder(root);
    }
    return 0;
}