分治-二叉樹重建

</pre><pre name="code" class="cpp">#include <iostream>
#include <sstream>
#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <stack>
#include <queue>
#include <set>
#include <math.h>
#include <time.h>

/*=======================================
二叉樹重建
老掉牙的話題
========================================*/
#define flush(arr, i) memset(arr, i, sizeof(arr))
typedef long long int64;
using namespace std;
const int MAX_ITEM = 1024;
const int oo = 0x7fffffff;
//const int oo = 0x3f3f3f3f;

char preOrder[MAX_ITEM] = "abcdefghij", inOrder[MAX_ITEM] = "cbedfahgji";

struct Node
{
    char data;
    Node *lchild, *rchild;
    Node(char key):data(key), lchild(NULL), rchild(NULL){}
};

//入口參數表示當前子樹的preOrder和inOrder
Node* reBuild(int inl, int inr, int pl, int pr)
{
    if(pr < pl)
        return NULL;

    Node *root = new Node(preOrder[pl]);
    //pos是inOrder序列中的位置，範圍注意
    int pos = inl;
    while(pos <= inr && inOrder[pos] != preOrder[pl])
        pos++;
    int len = pos - inl;
    //分治法
    root->lchild = reBuild(inl, pos - 1, pl + 1, pl + len);
    root->rchild = reBuild(pos + 1, inr, pl + len + 1, pr);
    return root;
}

//廣義表輸出
void traverse(Node *root)
{
    root == NULL ? printf("*") : printf("%c", root->data);
    if(!root)
        return;
    printf("(");
    traverse(root->lchild);
    printf(",");
    traverse(root->rchild);
    printf(")");
}

int main()
{
    Node *root = reBuild(0, 9, 0, 9);
    traverse(root);
    return 0;
}