先序遍历和中序遍历创建二叉树

 #include <iostream> #include <cstdio> #include <cstring> #define N 50 using namespace std; struct node_t {    char data;    struct node_t *lchild;    struct node_t *rchild;    node_t() {};    node_t(char ch, node_t *l = NULL, node_t *r = NULL)     : data(ch), lchild(l), rchild(r)     {     } }; node_t* build_tree(int n, char *pre_str, char *in_str) {    if(n <= 0)        return NULL;    int l_len = strchr(in_str, pre_str[0]) - in_str;    int r_len = n - l_len - 1;    node_t *root = new node_t(pre_str[0]);    root->lchild = build_tree(l_len, pre_str + 1, in_str);    root->rchild = build_tree(r_len, pre_str + l_len + 1, in_str + l_len + 1);    return root; } void visit(node_t *p) {     if(p != NULL)        printf("%c", p->data); } void pre_traverse(node_t *T) {     node_t *stack[N], *p = T;     int top = -1;     while(p != NULL || top != -1) {        while(p != NULL) {            visit(p);            stack[++top] = p;            p = p->lchild;        }        p = stack[top--];        p = p->rchild;     } } void lay_traverse(node_t *T) {     node_t *queen[N], *p;     int front, rear;     if( T != NULL) {        queen[0] = T;        front = -1;        rear = 0;        while(front < rear) {            p = queen[++front];            visit(p);            if(p->lchild != NULL)                queen[++rear] = p->lchild;            if(p->rchild != NULL)                queen[++rear] = p->rchild;        }     } } void in_traverse(node_t *T) {     node_t *stack[N], *p = T;     int top = -1;     while(p != NULL || top != -1) {        while(p != NULL) {            stack[++top] = p;            p = p->lchild;        }        p = stack[top--];        visit(p);        p = p->rchild;     } } void post_traverse(node_t *T) {     node_t *stack[N], *p = T;     int stack_flag[N];     int flag, top = -1;     while(p != NULL || top != -1) {        while(p != NULL) {            stack[++top] = p;            stack_flag[top] = 0;            p = p->lchild;        }        p = stack[top];        flag = stack_flag[top--];        if(flag == 0) {            stack[++top] = p;            stack_flag[top] = 1;            p = p->rchild;        } else {            visit(p);            p = NULL;        }     } } int tree_depth(node_t *T) {     if(T == NULL)        return 0;     else {        int ldepth = tree_depth(T->lchild);        int rdepth = tree_depth(T->rchild);        if(ldepth > rdepth)            return ldepth + 1;        else            return rdepth + 1;     } } int tree_depth2(node_t *T) {     node_t *stack[N], *p = T;     int stack_depth[N];     int curdepth, maxdepth = 0, top = -1;     if(p != NULL) {        curdepth = 1;        while(p != NULL || top != -1) {            while(p != NULL) {                stack[++top] = p;                stack_depth[top] = curdepth;                curdepth++;                p = p->lchild;            }            p = stack[top];            curdepth = stack_depth[top--];            if(p->lchild == NULL && p->rchild == NULL) {                if(curdepth > maxdepth)                    maxdepth = curdepth;            }            curdepth++;            p = p->rchild;        }     }     return maxdepth; } int node_depth(node_t *T, char key) {     node_t *stack[N], *p = T;     int stack_flag[N];     int flag, top = -1;     while(p != NULL || top != -1) {        while(p != NULL) {            stack[++top] = p;            stack_flag[top] = 0;            p = p->lchild;        }        p = stack[top];        flag = stack_flag[top--];        if(flag == 0) {            stack[++top] = p;            stack_flag[top] = 1;            p = p->rchild;        } else {            if(p->data == key)                return top + 2;            p = NULL;        }     } } int main() {     char pre_str[N], in_str[N];     int in_len;     while(scanf("%s%s", pre_str, in_str) != EOF) {        in_len = strlen(pre_str);        node_t *root = build_tree(in_len, pre_str, in_str);        printf("先序遍历：");        pre_traverse(root);        printf("\n");        printf("中序遍历：");        in_traverse(root);        printf("\n");        printf("后序遍历：");        post_traverse(root);        printf("\n");        printf("层次遍历：");        lay_traverse(root);        printf("\n");        printf("depth = %d\n", tree_depth(root));        printf("depth2 = %d\n", tree_depth2(root));        printf("node %c depth = %d\n", 'c', node_depth(root, 'c'));     }     return 0; }