1086已知中序先序求後序

#include<iostream>
#include<queue>
#include<stack>
#include<string>
#include<string.h>
#include<cstring>
using namespace std;

int pre[30];
int ino[30];
int flag = 1;

struct TreeNode
{
  int data;
  TreeNode* lefttree;
  TreeNode* righttree;
};

TreeNode *createTree(int pl, int pr, int il, int ir)
{
  if (pl > pr) return NULL;
  int i = 0;
  for (i = il; ino[i] != pre[pl]; i++);
  TreeNode *tree = (TreeNode*)malloc(sizeof(TreeNode));
  tree->data = pre[pl];
  tree->lefttree = createTree(pl + 1, pl + i - il, il, i - 1);
  tree->righttree = createTree(pl + i - il + 1, pr, i + 1, ir);
  if (flag == 1)
  {
    printf("%d", tree->data);
    flag = 2;
  }
  else
  {
    printf(" %d", tree->data);
  }
  return tree;
}
int main()
{
    int n, i = 0, j = 0;;
    stack<int> s;
    char str[4];
    scanf("%d", &n);
    scanf("%s %d", &str, &pre[i]);
    s.push(pre[0]);
    i++;
    while (j < n)
    {
      scanf("%s", &str);
      if (string(str) == "Push")
      {
        scanf("%d", &pre[i]);
        s.push(pre[i]);
        i++;
      }
      else if (string(str) == "Pop")
      {
        ino[j] = s.top();
        s.pop();
        j++;
      }
    }
    TreeNode *root = createTree(0, n - 1, 0, n - 1);
  return 0;
}
 

1020已知中序後序求先序

#include<iostream>
#include<queue>
using namespace std;

int pos[30];
int ino[30];

struct TreeNode
{
  int data;
  TreeNode* lefttree;
  TreeNode* righttree;
};

TreeNode *createTree(int pl,int pr,int il,int ir)
{
  if (pl > pr) return NULL;
  TreeNode* tree;
  int i = 0;
  for (i = il; i < ir, pos[pr] != ino[i]; i++);
  tree = (TreeNode*)malloc(sizeof(TreeNode));
  tree->data = pos[pr];
  tree->lefttree = createTree(pl, pl + i - 1 - il, il, i - 1);
  tree->righttree = createTree(pl + i - il, pr - 1, i + 1, ir);
  return tree;
}
int main()
{
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
    {
      scanf("%d", &pos[i]);
    }
    for (int i = 0; i < n; i++)
    {
      scanf("%d", &ino[i]);
    }
    TreeNode *root=createTree(0,n-1,0,n-1);
    queue<TreeNode*> que;
    que.push(root);
    printf("%d", root->data);
    int j = 0;
    while (!que.empty())
    {
      TreeNode *t = que.front();
        if (j != 0 && t != NULL)
        {
          printf(" %d", t->data);
        }
        j = 2;
        que.pop();
        if (t->lefttree != NULL)
        {
          que.push(t->lefttree);
        }
        if (t->righttree != NULL)
        {
          que.push(t->righttree);
        }
    }
  return 0;
}
 

1119已知先序後序求中序

// ConsoleApplication2.cpp : 定義控制檯應用程式的入口點。
#include "stdafx.h"


#include<iostream>
#include<queue>
#include<stack>
#include<string>
#include<string.h>
#include<cstring>
#include<vector>
using namespace std;

int pre[30];
int pos[30];
int ino[30];
int k = 0;

int CreateTree(int l1,int r1,int l2,int r2)
{
	if (l1 > r1) return 0;//如果沒有某一子節點，則中序遍歷不唯一
	if (l1 == r1)//如果沒有任意子節點，則在這裡截胡，直接存入陣列返回1
	{
		ino[k++] = pre[l1];
		return 1;
	}
	int i = 0;
	for ( i = l2; pre[l1+1] != pos[i]; i++);//找到自己子節點中的根節點
	int ok = 1;
	ok &= CreateTree(l1 + 1, l1 + 1 + i - l2, l2, i);//在後序中，找到的該根節點及其之前的節點為當前結點的左孩子
	ino[k++]=pre[l1];//中序遍歷嘛，這裡存入資料
	ok &= CreateTree(l1 + 2 + i - l2, r1, i + 1, r2 - 1);//在後序中，找到的該根節點之後的節點，不包括該根節點，為當前節點的右孩子（l1+2+i-l2是左邊界，該邊界由i定義，而右邊界為r1，與i無關，所以前面return0的判斷條件那麼寫，就是我不管你有沒有左右節點，我都往下傳，判斷沒有則返回0）
	return ok;
}

int main()
{
	
	while (1)
	{
		int n;
		scanf("%d", &n);
		for (int i = 1; i <=n; i++)
		{
			scanf("%d", &pre[i]);
		}
		for (int i = 1; i <= n; i++)
		{
			scanf("%d", &pos[i]);
		}
		int ok=CreateTree(1, n, 1, n);
		ok ? printf("Yes") : printf("No");
		printf("\n");
		for (int i = 0; i < k; i++)
		{
			if (i==0)
			{
				printf("%d", ino[i]);
			}
			else
			{
				printf(" %d", ino[i]);
			}
		}
	}
	return 0;
}