poj2255Tree Recovery【二叉树重构】
大意：告诉你一棵二叉树的先序遍历和中序遍历求该二叉树的后续遍历
代码：
1 #include <iostream> 2 #include <cstdio> 3 #include <cstring> 4 using namespace std; 5 6 const int maxn = 30; 7 char pr[maxn], mi[maxn]; 8 9 struct Node { 10 int left; 11 int right; 12 }tr[maxn]; 13 14 int root; 15 16 void init(int p) { 17 tr[p].left = -1; 18 tr[p].right = -1; 19 } 20 21 void fason(int pa, int son) { 22 if(son < pa) { 23 if(tr[pa].left == -1) { 24 init(son); 25 tr[pa].left = son; 26 } else fason(tr[pa].left, son); 27 } else { 28 if(tr[pa].right == -1) { 29 init(son); 30 tr[pa].right = son; 31 } else fason(tr[pa].right, son); 32 } 33 } 34 35 void build_tree() { 36 for(int i = 0; mi[i]; i++) { 37 if(mi[i] == pr[0]) { 38 root = i; 39 init(root); 40 break; 41 } 42 } 43 for(int i =1; pr[i]; i++) { 44 for(int j = 0; mi[j]; j++) { 45 if(mi[j] == pr[i]) { 46 fason(root, j); 47 break; 48 } 49 } 50 } 51 } 52 void pre_out(int p) { 53 printf("%c", mi[p]); 54 if(tr[p].left != -1) pre_out(tr[p].left); 55 if(tr[p].right != -1) pre_out(tr[p].right); 56 } 57 void mid_out(int p) { 58 if(tr[p].left != -1) mid_out(tr[p].left); 59 printf("%c", mi[p]); 60 if(tr[p].right != -1) mid_out(tr[p].right); 61 } 62 63 void back_out(int p) { 64 if(tr[p].left != -1) back_out(tr[p].left); 65 if(tr[p].right != -1) back_out(tr[p].right); 66 printf("%c", mi[p]); 67 } 68 69 int main() { 70 while(EOF != scanf("%s %s",pr, mi) ) { 71 build_tree(); 72 pre_out(root); 73 puts(""); 74 mid_out(root); 75 puts(""); 76 back_out(root); 77 puts(""); 78 } 79 return 0; 80 }
