按广义表表示二叉树结构生成二叉链表的算法

bintnode* createtree(char* str) {
    bintnode* st[100];
    bintnode* p = NULL;
    int top, k, j = 0;
    top = -1;
    char ch = str[j];
    bintnode* b = NULL;
    while (ch != '\0') {
        switch (ch) {
        case'(':top++; st[top] = p; k = 1; break;
        case')':top--; break;
        case',':k = 2; break;
        default:p = (bintnode*)malloc(sizeof(bintnode));
            p->data = ch;
            p->lchild = p->rchild = NULL;
            if (b == NULL)
                b = p;
            else {
                switch (k) {
                case 1:st[top]->lchild = p; break;
                case 2:st[top]->rchild = p; break;
                }
            }
        }
        j++; ch = str[j];
    }
    return b;
}