1115. Counting Nodes in a BST (30)
A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:
- The left subtree of a node contains only nodes with keys less than or equal to the node's key.
- The right subtree of a node contains only nodes with keys greater than the node's key.
- Both the left and right subtrees must also be binary search trees.
Insert a sequence of numbers into an initially empty binary search tree. Then you are supposed to count the total number of nodes in the lowest 2 levels of the resulting tree.
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (<=1000) which is the size of the input sequence. Then given in the next line are the N integers in [-1000 1000] which are supposed to be inserted into an initially empty binary search tree.
Output Specification:
For each case, print in one line the numbers of nodes in the lowest 2 levels of the resulting tree in the format:
n1 + n2 = n
where n1 is the number of nodes in the lowest level, n2 is that of the level above, and n is the sum.
Sample Input:9 25 30 42 16 20 20 35 -5 28Sample Output:
2 + 4 = 6
//1115. Counting Nodes in a BST(30)
#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int a[1001] = { 0 }, level=-1;
typedef struct node {
int data;
node *l, *r;
}*Tree;
Tree T;
void createtree(Tree &T,int num) {
if (T == NULL) {
T = new node();
T->data = num;
T->l = NULL;
T->r = NULL;
return;
}
if (num <= T->data)
createtree(T -> l, num);
else createtree(T->r, num);
}
void dfs(Tree T,int depth) {
if (T == NULL) return;
a[depth]++;
level = max(level, depth);
dfs(T->l, depth+1);
dfs(T->r, depth+1);
}
int main() {
int n,in[1001];
cin >> n;
for (int i = 0; i < n; i++) {
cin >> in[i];
createtree(T, in[i]);
}
dfs(T, 0);
printf("%d + %d = %d\n", a[level], a[level - 1], a[level] + a[level - 1]);
return 0;
}