题目链接:https://vjudge.net/problem/UVA-536
题目大意
多组数据,每组数据给定一个二叉树的先序遍历和中序遍历,求后序遍历。遍历串字符为大写字母,不重复出现。
分析
二叉树基础题。
代码如下
1 #include <bits/stdc++.h> 2 using namespace std; 3 4 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); 5 #define Rep(i,n) for (int i = 0; i < (n); ++i) 6 #define For(i,s,t) for (int i = (s); i <= (t); ++i) 7 #define rFor(i,t,s) for (int i = (t); i >= (s); --i) 8 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i) 9 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i) 10 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i) 11 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i) 12 13 #define pr(x) cout << #x << " = " << x << " " 14 #define prln(x) cout << #x << " = " << x << endl 15 16 #define LOWBIT(x) ((x)&(-x)) 17 18 #define ALL(x) x.begin(),x.end() 19 #define INS(x) inserter(x,x.begin()) 20 21 #define ms0(a) memset(a,0,sizeof(a)) 22 #define msI(a) memset(a,inf,sizeof(a)) 23 #define msM(a) memset(a,-1,sizeof(a)) 24 25 #define MP make_pair 26 #define PB push_back 27 #define ft first 28 #define sd second 29 30 template<typename T1, typename T2> 31 istream &operator>>(istream &in, pair<T1, T2> &p) { 32 in >> p.first >> p.second; 33 return in; 34 } 35 36 template<typename T> 37 istream &operator>>(istream &in, vector<T> &v) { 38 for (auto &x: v) 39 in >> x; 40 return in; 41 } 42 43 template<typename T1, typename T2> 44 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) { 45 out << "[" << p.first << ", " << p.second << "]" << " "; 46 return out; 47 } 48 49 inline int gc(){ 50 static const int BUF = 1e7; 51 static char buf[BUF], *bg = buf + BUF, *ed = bg; 52 53 if(bg == ed) fread(bg = buf, 1, BUF, stdin); 54 return *bg++; 55 } 56 57 inline int ri(){ 58 int x = 0, f = 1, c = gc(); 59 for(; c<48||c>57; f = c=='-'?-1:f, c=gc()); 60 for(; c>47&&c<58; x = x*10 + c - 48, c=gc()); 61 return x*f; 62 } 63 64 typedef long long LL; 65 typedef unsigned long long uLL; 66 typedef pair< double, double > PDD; 67 typedef pair< int, int > PII; 68 typedef pair< int, PII > PIPII; 69 typedef pair< string, int > PSI; 70 typedef pair< int, PSI > PIPSI; 71 typedef set< int > SI; 72 typedef vector< int > VI; 73 typedef vector< VI > VVI; 74 typedef vector< PII > VPII; 75 typedef map< int, int > MII; 76 typedef map< int, PII > MIPII; 77 typedef map< string, int > MSI; 78 typedef multimap< int, int > MMII; 79 typedef unordered_map< int, int > uMII; 80 typedef pair< LL, LL > PLL; 81 typedef vector< LL > VL; 82 typedef vector< VL > VVL; 83 typedef priority_queue< int > PQIMax; 84 typedef priority_queue< int, VI, greater< int > > PQIMin; 85 const double EPS = 1e-10; 86 const LL inf = 0x7fffffff; 87 const LL infLL = 0x7fffffffffffffffLL; 88 const LL mod = 1e9 + 7; 89 const int maxN = 1e4 + 7; 90 const LL ONE = 1; 91 const LL evenBits = 0xaaaaaaaaaaaaaaaa; 92 const LL oddBits = 0x5555555555555555; 93 94 string preorder, inorder, postorder; 95 96 // pre: preorder子串的起始位置 97 // in: inorder子串的起始位置 98 // len: 子串长度 99 void solve(int pre, int in, int len) { 100 if(len <= 0) return; 101 postorder.insert(0, 1, preorder[pre]); 102 int pos = inorder.find(preorder[pre]) - in; 103 104 solve(pre + pos + 1, in + pos + 1, len - pos - 1); 105 solve(pre + 1, in, pos); 106 } 107 108 int main(){ 109 //freopen("MyOutput.txt","w",stdout); 110 INIT(); 111 while(cin >> preorder >> inorder) { 112 postorder = ""; 113 solve(0, 0, preorder.size()); 114 cout << postorder << endl; 115 } 116 return 0; 117 }