查找与排序算法（Searching adn Sorting）

1，查找算法

　　常用的查找算法包括顺序查找，二分查找和哈希查找。

　　1.1 顺序查找(Sequential search)

　　　　顺序查找： 依次遍历列表中每一个元素，查看是否为目标元素。python实现代码如下：　　

#无序列表
def sequentialSearch(alist,item):
    found = False
    pos=0
    while not found and pos<len(alist):
        if alist[pos]==item:
            found=True
        else:
            pos = pos+1
    return found
testlist = [1, 2, 32, 8, 17, 19, 42, 13, 0]
print(sequentialSearch(testlist, 3))
print(sequentialSearch(testlist, 13))

#有序列表(升序)
def orderedSequentialSearch(orderedList,item):
    found = False
    pos = 0
    stop = False
    while not found and not stop and pos<len(orderedList):
        if orderedList[pos]==item:
            found=True
        else:
            if orderedList[pos]>item:
                stop=True
            else:
                pos = pos+1
    return found
testlist = [0, 1, 2, 8, 13, 17, 19, 32, 42,]
print(orderedSequentialSearch(testlist, 3))
print(orderedSequentialSearch(testlist, 13))

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