样例:
a
/
b f
c g
/
d
e
此二叉树前序序列为;abcdefg中序序列为:bdecafc
思路:先观察前序第一个节点a,其必为树的根;中序序列里节点a之前的节点构成节点a的左子树,剩下的节点为节点a的右子树;对于左右子树同样重复上面的步骤判断即可。
#include <stdio.h> #include <stdlib.h> //由前序序列、中序序列重建二叉树 void reconstruct_tree(char *pre, char* in, int i, treenode** T){ int k; if(i==0){ *T = NULL; return; } else{ if((*T=(treenode*)malloc(sizeof(treenode)))==NULL){ printf("malloc failed "); exit(0); } else{ (*T)->data = *pre; (*T)->lc = NULL; (*T)->rc = NULL; k=0; if(*pre!=*in){ for(k=0; k<i; k++){ if(*pre==*(in+k)){ break; } } reconstruct_tree(pre+1, in, k, &(*T)->lc); } if(k<i){ reconstruct_tree(pre+k+1, in+k+1, i-k-1, &(*T)->rc); } } } } int main(void) { treenode *mytree=NULL; tlist *mytlist=NULL; int i,k; char *pre, *in; scanf("%d", &i); if((pre=(char*)malloc(sizeof(char)*i))==NULL){ printf("malloc failed "); exit(0); } if((in=(char*)malloc(sizeof(char)*i))==NULL){ printf("malloc failed "); exit(0); } for(k=0; k<i; k++){ fflush(stdin); scanf("%c", pre+k); } for(k=0; k<i; k++){ fflush(stdin); scanf("%c", in+k); } reconstruct_tree(pre, in, i, &mytree); pre_visit_tree(mytree); printf(" "); system("pause"); return 0; }