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July 24, 2017 05:48
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14. 什么是数据结构? - 作业四
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| require 'benchmark' | |
| def binary_search(arr, element) | |
| arr.sort! | |
| start_val = 0 | |
| end_val = arr.length - 1 | |
| while start_val <= end_val | |
| mid = start_val + (end_val - start_val) / 2; | |
| if arr[mid] < element | |
| start_val = mid + 1 | |
| elsif (arr[mid] > element) | |
| end_val = mid - 1 | |
| else | |
| return mid | |
| end | |
| end | |
| puts "not found." | |
| end | |
| arr = [0, 5, 13, 13, 30, 42, 52, 70, 85, 96, 103, 111, 116, 127, 130, 143, 150, 150, 161, 175, 207, 210, 218, 246, 257, 257, 263, 280, 304, 310, 326, 327, 332, 346, 360, 371, 374, 378, 406, 407, 407, 408, 428, 431, 437, 442, 445, 479, 489, 491, 505, 517, 520, 536, 548, 598, 602, 605, 618, 642, 649, 654, 659, 662, 677, 678, 682, 689, 695, 696, 697, 701, 711, 717, 727, 737, 745, 749, 754, 757, 770, 786, 802, 805, 814, 832, 840, 850, 853, 854, 888, 894, 904, 913, 913, 945, 962, 964, 972, 998] | |
| # 应该回传 35 | |
| puts arr.find_index(arr.bsearch {|x| x >= 371 }) | |
| puts binary_search(arr, 371).to_s | |
| Benchmark.bm do |x| | |
| x.report { | |
| binary_search(arr, 371) | |
| } | |
| x.report { | |
| arr.find_index(arr.bsearch {|x| x >= 371 }) | |
| } | |
| end | |
| arr1 = Array.new(10) { |param| param = rand(10)} # each 和 块 里面处理逻辑不太懂，尤其这个赋值，看书后理解的这样写，但是下面那样才简洁 | |
| arr2 = Array.new(10000) { rand(10000)} | |
| arr3 = Array.new(1000000) {rand(1000000)} | |
| puts binary_search(arr1, 9).to_s | |
| puts binary_search(arr2, 1234).to_s | |
| puts binary_search(arr3, 123456).to_s | |
| Benchmark.bm do |x| | |
| x.report { | |
| binary_search(arr1, 9) | |
| } | |
| x.report { | |
| binary_search(arr2,1234) | |
| } | |
| x.report { | |
| binary_search(arr3, 123456) | |
| } | |
| end |
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