标签：amp tchar bsp tree 中序 def algorithm 中序遍历 取反
emmm....这道题的意思比较清楚,就是叫我们先中序后序建树,然后层序遍历,但是这个层序遍历每一层遍历次序都要相反
中需后续建树就不用说了,不会的拖出去打三十大板再回来...需要注意的就是可以用哈希表优化一下查找,即用unordered_map容器
预先存储中序遍历中每个数的位置,查找就不用循环了。
然后就是如何层序遍历取反了,其实还是可以用层序遍历的公式,一层一层得处理(循环开始时用size储存该层的个数,然后循环size次),
只不过是用双端队列deque容器,这个容器支持两边出队和入队,然后用一个flg标记一下就好啦
代码:
#include<iostream> #include<string> #include<map> #include<set> #include<algorithm> #include<queue> #include<cmath> #include<string.h> #include<unordered_map> #include<unordered_set> using namespace std; #define INT_MIN -2147483648 #define INT_MAX 2147483647 const int maxn = 35; int read() { char p; while ((p = getchar()) < ‘0‘ || p > ‘9‘); int sum = p - 48; while ((p = getchar()) >= ‘0‘ && p <= ‘9‘)sum = sum * 10 + p - ‘0‘; return sum; } int tree[maxn][2]; int val[maxn]; int tot = 0; unordered_map<int, int>M; vector<int>v[2]; int n; int build(int st1, int ed1, int st2, int ed2) { if (st1 > ed1)return -1; val[++tot] = v[0][ed1]; int rt = tot; int pos = M[v[0][ed1]]; tree[rt][0] = build(st1, pos - st2 + st1-1, st2, pos-1); tree[rt][1] = build(pos - st2 + st1, ed1 - 1, pos + 1, ed2); return rt; } void level_order(int rt) { deque<int>Q; Q.push_back(rt); bool flg = 0,h=0; int t; while (!Q.empty()) { int size = Q.size(); for (int k = 0; k <size; k++) { if (flg) { t = Q.front(); Q.pop_front(); if (tree[t][0] != -1)Q.push_back(tree[t][0]); if (tree[t][1] != -1)Q.push_back(tree[t][1]); } else { t = Q.back(); Q.pop_back(); if (tree[t][1] != -1)Q.push_front(tree[t][1]); if (tree[t][0] != -1)Q.push_front(tree[t][0]); } if (h)printf(" "); printf("%d", val[t]); h = 1; } flg = !flg; } } int main() { //freopen("test.txt", "r", stdin); n = read(); v[0].resize(n); v[1].resize(n); //cout << 1 << endl; for (int i = 0; i < n; i++) { v[1][i] = read(); M[v[1][i]] = i; } for (int i = 0; i < n; i++) { v[0][i] = read(); } //cout << 2 << endl; int root=build(0,n-1,0,n-1); level_order(root); return 0; }
1127 ZigZagging on a Tree(PAT)
标签：amp tchar bsp tree 中序 def algorithm 中序遍历 取反
原文地址：https://www.cnblogs.com/MYMYACMer/p/14346426.html
