1006. Tree Traversals - Hard Version (35)解题报告
来源:互联网 发布:sql server报价 编辑:程序博客网 时间:2024/06/05 01:16
感谢神赐予我智慧和力量来解决这道题。
这道题对时间要求不高,用暴力DFS+适当的剪枝就可以解决。
中序LMR、前序MLR、后序LRM遍历序列有这样的性质,需要遍历的树上的任何一棵子树前序遍历序列的第一个元素等于后序遍历序列的最后一个元素,且该元素在中序遍历中恰好把根的左子树和右子树分割开来。
做题过程中参考了以下两篇博文:
PAT (Top Level) Practise 1006 Tree Traversals - Hard Version (35)
1006. Tree Traversals - Hard Version (35)
#define _CRT_SECURE_NO_WARNINGS#include <cstdio>#include <cstdlib>#include <cstring>#include <cctype>#include <queue>using namespace std;const int maxn = 110;int inorder[maxn], preorder[maxn], postorder[maxn], t[maxn], tree[maxn][2], f[maxn], root;int rein[maxn], repre[maxn], repost[maxn];bool flag;bool dfs(int &index, int inl, int inr, int prel, int prer, int postl, int postr);void dfs(int root, int p);void bfs(void);int get(void);int main(void) {int i, n, cnt = 0, residue;scanf("%d", &n);for (i = 1; i <= n; i++) inorder[i] = get(), f[inorder[i]]++, rein[inorder[i]] = i;for (i = 1; i <= n; i++) preorder[i] = get(), f[preorder[i]]++, repre[preorder[i]] = i;for (i = 1; i <= n; i++) postorder[i] = get(), f[postorder[i]]++, repost[postorder[i]] = i;for (i = 1; i <= n; i++) if (!f[i]) cnt++, residue = i;if(cnt > 1 || !dfs(root, 1, n, 1, n, 1, n)) puts("Impossible");else {for (i = 1; i <= n; i++) if (!t[i]) t[i] = residue;flag = 0, dfs(root, 2), putchar('\n');flag = 0, dfs(root, 1), putchar('\n');flag = 0, dfs(root, 3), putchar('\n');flag = 0, bfs();}return 0;}bool dfs(int &index, int inl, int inr, int prel, int prer, int postl, int postr) {int i, tmp;if (inl > inr) {index = 0; return true;}for (i = inl; i <= inr; i++) {if (inorder[i] && preorder[prel] && inorder[i] != preorder[prel]) continue;if (inorder[i] && postorder[postr] && inorder[i] != postorder[postr]) continue;if (preorder[prel] && postorder[postr] && preorder[prel] != postorder[postr]) return false;tmp = max(inorder[i], max(preorder[prel], postorder[postr]));if (rein[tmp] && rein[tmp] != i) continue;if (repre[tmp] && repre[tmp] != prel) continue;if (repost[tmp] && repost[tmp] != postr) continue;if (!dfs(tree[i][0], inl, i - 1, prel + 1, prel + i - inl, postl, postl + i - inl - 1)) continue;if (!dfs(tree[i][1], i + 1, inr, prel + i - inl + 1, prer, postl + i - inl, postr - 1)) continue;index = i;t[index] = tmp;return true;}return false;}void dfs(int root, int p) {if (!root) return;if (p == 1) printf("%s%d", flag ? " " : "", t[root]), flag = true;dfs(tree[root][0], p);if (p == 2) printf("%s%d", flag ? " " : "", t[root]), flag = true;dfs(tree[root][1], p);if (p == 3) printf("%s%d", flag ? " " : "", t[root]), flag = true;return;}void bfs(void) {queue<int> q;int tmp;q.push(root);printf("%d", t[root]);while (!q.empty()) {tmp = q.front();q.pop();if (tree[tmp][0]) q.push(tree[tmp][0]), printf(" %d", t[tree[tmp][0]]);if (tree[tmp][1]) q.push(tree[tmp][1]), printf(" %d", t[tree[tmp][1]]);}return;}int get(void) {int tmp, i;char str[10];scanf("%s", str);if (str[0] == '-') {return 0;}else {tmp = 0;for (i = 0; str[i]; i++) {tmp = tmp * 10 + str[i] - '0';}return tmp;}}
0 0
- 1006. Tree Traversals - Hard Version (35)解题报告
- 1006. Tree Traversals - Hard Version (35)
- PAT (Top Level) Practise 1006 Tree Traversals - Hard Version (35)
- 1001. Battle Over Cities - Hard Version (35)解题报告
- 解题报告-PAT- Tree Traversals Again(1086)
- 1086. Tree Traversals Again (25)解题报告
- PAT(Advanced Level) 1020 Tree Traversals 解题报告
- 1004. To Buy or Not to Buy - Hard Version (35)解题报告
- 【LeetCode】99.Recover Binary Search Tree(Hard)解题报告
- 【LeetCode】145.Binary Tree Postorder Traversal(Hard)解题报告
- 1007. Red-black Tree (35)解题报告
- Tree Recovery解题报告
- poj1741 Tree解题报告
- [bzoj3282]tree 解题报告
- [poj1741]tree 解题报告
- A - A hard puzzle解题报告
- 【LeetCode】135.Candy(hard)解题报告
- 【LeetCode】403. Frog Jump(Hard)解题报告
- 腾讯XLua 03-CSharp Invoke Lua
- centos命令
- 栈的压入、弹出序列
- cookie的作用范围
- mysql学习之连接查询
- 1006. Tree Traversals - Hard Version (35)解题报告
- 程序员面试金典——解题总结: 9.17中等难题 17.1编写一个函数,不用临时变量,直接交换两个数
- r语言中时间函数处理
- 面向对象
- 自定义图片比例适配控件 ProportionImageView
- 第三章——构建模块
- 仪表盘和图形编辑器 Grafana
- 安装WinXp时遇到蓝屏(BAD_POLL_CALLER)
- 递归问题深入到堆栈小结