数据结构与算法分析——c语言描述 练习4.19  答案

挺有意思的。改递归为非递归。其实原理还是一样，都用了栈。

AvlTree insert(ElementType X, AvlTree t) {
    AvlTree root = t;
    std::stack<AvlTree> route;
    
    while (1) {
        if (t == NULL) {
            t = (AvlTree)malloc(sizeof(struct AvlNode));
            if (t == NULL)
                Error("out of memory");
            t->element = X;
            t->left = NULL;
            t->right = NULL;
            t->height = 0;
            t->isDeleted = 0;
            route.push(t);
            break;
        }
        else if (X < retrieve(t)) {
            route.push(t);
            t = t->left;
            continue;
        }
        else if (X >retrieve(t)) {
            route.push(t);
            t = t->right;
            continue;
        }
        else {
            t->isDeleted = 0;
            return root;
        }
    }

    AvlTree father,son;
    while (1) {
        son = route.top();
        route.pop();
        if (route.empty())
            return son;
        father = route.top();
        route.pop();
        if (father->element < son->element) {//儿子在右边
            father->right = son;
            if (height(father->right) - height(father->left) == 2) {
                if (X > retrieve(father->right))
                    father = singleRotateWithRight(father);
                else
                    father = doubleRotateWithRight(father);
            }
            route.push(father);
        }
        else if (father->element > son->element) {//儿子在左边
            father->left = son;

            if (height(father->left) - height(father->right) == 2) {
                if (X < retrieve(father->left)) {
                    father = singleRotateWithLeft(father);
                }
                else
                    father = doubleRotateWithLeft(father);
            }
            route.push(father);
        }
        father->height = Max(height(father->left), height(father->right)) + 1;
    }

    
    
}