C：不要在for循环内定义变量，在函数开始处定义变量

#include
      
       #include
       
        #include
        
         typedef struct tree{    int data ;    struct tree *l, *r ;}tree, *tr ;int flag ;tr creat(int *root, int*in, int k){    tr t ;    int *p ,m;    if(k<=0)    return NULL ;    t = (struct tree*)malloc(sizeof(struct tree)) ;    t->data = *root ;    for(p=in; p!=NULL; p++)    if(*p==*root)    break ;    m = p - in ;    t->l = creat(root+1, in, m) ;    t->r = creat(root+m+1, p+1, k-m-1) ;    return t ;}void postorder(tr t){    if(t!=NULL)    {        postorder(t->l) ;        postorder(t->r) ;        if(flag)        printf(" ") ;        flag = 1 ;        printf("%d", t->data) ;    }}int main(){    tr t ;    int  n,i ;    int root[1001], in[1001] ;    while(scanf("%d", &n)!=EOF)    {        flag = 0 ;        for(i=0; i
        
       
      

C++：

#include
      
       using namespace std;typedef struct tree{ int data; struct tree *r,*l;}tree,*tr;int flag;tr creat(int *a,int *b,int n){ tr s; int *p,k; if(n <= 0) return NULL; s = new tree; s->data = *a; for(p=b; p!=NULL; p++) {  if(*p == *a) break; } k = p - b; s->l = creat(a + 1,b,k); s->r = creat(a + k + 1,p + 1,n - k - 1); return s;}void postorder(tr b){ if(b != NULL) {  postorder(b->l);  postorder(b->r);  if(flag)  cout<<" ";  flag = 1;  cout<
       
        data; }}int main(){ int a[1001],b[1001]; int n; while(cin>>n) {  flag = 0;  for(int i = 0;i < n;i ++)  cin>>a[i];  for(int i = 0;i < n;i ++)  cin>>b[i];  postorder(creat(a,b,n));  cout<
       
      

注意输入输出格式,已知先序和中序，求后序