No Greater Than X in BST

最新推荐文章于 2020-09-13 07:45:30 发布

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本文介绍了一种在二叉搜索树中查找所有不大于给定值X的元素的算法，并通过递减顺序输出这些元素。该算法使用了迭代而非递归的方法，有效地实现了题目要求的功能。

No Greater Than X in BST （20 分）

You are supposed to output, in decreasing order, all the elements no greater than X in a binary search tree T.

Format of function:

void Print_NGT( Tree T,  int X );

where Tree is defined as the following:

typedef struct TreeNode *Tree;
struct TreeNode {
    int Element;
    Tree  Left;
    Tree  Right;
};

The function is supposed to use Output(X) to print X.

Sample program of judge:

#include <stdio.h>
#include <stdlib.h>

typedef struct TreeNode *Tree;
struct TreeNode {
    int Element;
    Tree  Left;
    Tree  Right;
};

Tree BuildTree(); /* details omitted */
void Output( int X ); /* details omitted */

void Print_NGT( Tree T,  int X );

int main()
{
    Tree T;
    int X;

    T = BuildTree();
    scanf("%d", &X);
    Print_NGT( T, X );
    printf("End\n");

    return 0;
}

/* Your function will be put here */

Sample Output 1 (for the tree shown in Figure 1):

91 90 85 81 80 55 End

Sample Output 2 (for the tree shown in Figure 2):

End

void Print_NGT(Tree T, int X) {
   if (T == NULL) return;
   int e[10000];
   int c = -1;
   Tree f[10000];
   int t = -1;
   while (T != NULL || t>-1) {
       while (T != NULL) {
           f[++t] = T;
           T = T->Left;
       }
       if (t > -1) {
           T = f[t--];
           if (T->Element <= X) e[++c] = T->Element;
           T = T->Right;
       }
   }
   for (int i = c; i >= 0; i--)
       printf("%d ", e[i]);
}