前段时间为准备百度面试恶补的东西,虽然最后还是被刷了,还是把那几天的“战利品”放点上来,算法一直是自己比较薄弱的地方,以后还要更加努力啊。
下面用Python实现了几个常用的排序,如快速排序,选择排序,以及二路并归排序等等。
#encoding=utf-8 import random from copy import copydef directInsertSort(seq): """ 直接插入排序 """ size = len(seq) for i in range(1,size): tmp, j = seq[i], i while j > 0 and tmp < seq[j-1]: seq[j], j = seq[j-1], j-1 seq[j] = tmp return seq
def directSelectSort(seq): """ 直接选择排序 """ size = len(seq) for i in range(0,size - 1): k = i;j = i+1 while j < size: if seq[j] < seq[k]: k = j j += 1 seq[i],seq[k] = seq[k],seq[i] return seq
def bubbleSort(seq): """冒泡排序""" size = len(seq) for i in range(1,size): for j in range(0,size-i): if seq[j+1] < seq[j]: seq[j+1],seq[j] = seq[j],seq[j+1] return seq
def _divide(seq, low, high): """快速排序划分函数""" tmp = seq[low] while low != high: while low < high and seq[high] >= tmp: high -= 1 if low < high: seq[low] = seq[high] low += 1 while low < high and seq[low] <= tmp: low += 1 if low < high: seq[high] = seq[low] high -= 1 seq[low] = tmp return low
def _quickSort(seq, low, high): """快速排序辅助函数""" if low >= high: return mid = _divide(seq, low, high) _quickSort(seq, low, mid - 1) _quickSort(seq, mid + 1, high)
def quickSort(seq): """快速排序包裹函数""" size = len(seq) _quickSort(seq, 0, size - 1) return seq
def merge(seq, left, mid, right): tmp = [] i, j = left, mid while i < mid and j <= right: if seq[i] < seq[j]: tmp.append(seq[i]) i += 1 else: tmp.append(seq[j]) j += 1 if i < mid: tmp.extend(seq[i:]) if j <= right: tmp.extend(seq[j:])
seq[left:right+1] = tmp[0:right-left+1]
def _mergeSort(seq, left, right): if left == right: return else: mid = (left + right) / 2 _mergeSort(seq, left, mid) _mergeSort(seq, mid + 1, right) merge(seq, left, mid+1, right)
#二路并归排序 def mergeSort(seq): size = len(seq) _mergeSort(seq, 0, size - 1) return seq
if __name__ == '__main__': s = [random.randint(0,100) for i in range(0,20)] print s print "\n" print directSelectSort(copy(s)) print directInsertSort(copy(s)) print bubbleSort(copy(s)) print quickSort(copy(s)) print mergeSort(copy(s))
E:\python_project\practice>sorting.py [10, 47, 56, 76, 64, 84, 26, 8, 47, 51, 88, 81, 32, 95, 91, 29, 28, 69, 61, 45][8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95] [8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95] [8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95] [8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95] [8, 10, 26, 28, 29, 32, 45, 47, 47, 51, 56, 61, 64, 69, 76, 81, 84, 88, 91, 95]