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sicp 2.64 构建平衡二叉树
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;#lang planet neil/sicp | |
#lang racket | |
(require (planet soegaard/sicp:2:1/sicp)) | |
(define wave einstein) | |
(define (list-tree elements) | |
(car (partial-tree elements (length elements)))) | |
(define (partial-tree elts n) | |
(if (= n 0) | |
(cons '() elts) | |
(let ((left-size (quotient (- n 1) 2))) | |
(let ((left-result (partial-tree elts left-size))) | |
(let ((left-tree (car left-result)) | |
(non-left-elts (cdr left-result)) | |
(right-size (- n (+ left-size 1)))) | |
(let ((this-entry (car non-left-elts)) | |
(right-result (partial-tree (cdr non-left-elts) right-size))) | |
(let ((right-tree (car right-result)) | |
(remaining-elts (cdr right-result))) | |
(cons (make-tree this-entry left-tree right-tree) | |
remaining-elts)))))))) | |
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