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传送门:https://pintia.cn/problem-sets/994805342720868352/problems/994805380754817024
解:
前序遍历+中序遍历 恢复二叉树
Push的顺序是前序遍历
Pop的顺序是中序遍历
- #include<cstdio>
- #include<cstring>
- typedef struct node{
- int data;
- struct node *lchild, *rchild;
- node(){
- lchild = rchild = NULL;
- }
- } BTNode, *BTREE;
- int n, num, preorder[35], inorder[35];
- void input(void)
- {
- int stack[35], top = -1, pi = 0, ii = 0;;
- char s[5];
- scanf("%d", &n);
- for (int i = 0; i < 2 * n; i++)
- {
- scanf("%s", s);
- if (strcmp(s, "Push"))
- inorder[ii++] = stack[top--];
- else
- {
- scanf("%d", preorder + pi);
- stack[++top] = preorder[pi++];
- }
- }
- }
- int find(int target)
- {
- for (int i = 0; i < n; i++)
- if (inorder[i] == target)
- return i;
- }
- void insert(BTREE root, int pos)
- {
- if (!root) return;
- int parents = find(root->data);
- if (pos > parents)
- {
- if (root->rchild)
- insert(root->rchild, pos);
- else
- {
- root->rchild = new BTNode;
- root->rchild->data = inorder[pos];
- }
- }
- else
- {
- if (root->lchild)
- insert(root->lchild, pos);
- else
- {
- root->lchild = new BTNode;
- root->lchild->data = inorder[pos];
- }
- }
- }
- void print_postorder(BTREE root)
- {
- if (!root) return;
- print_postorder(root->lchild);
- print_postorder(root->rchild);
- printf("%d", root->data);
- if (++num < n) putchar(' ');
- }
- int main(void)
- {
- input();
- BTREE root = new BTNode;
- root->data = preorder[0];
- for (int i = 1; i < n; i++)
- insert(root, find(preorder[i]));
- print_postorder(root);
- return 0;
- }
复制代码
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