python中顺序查找分析和实现

　　顺序查找算法是一种很基本的查找算法，该算法的复杂度一般是最大是O(n)，假如加上顺序查找，算法的复杂度

还要降一倍，为O（n/2）。

　　Python的代码实现如下所示：

　　

def sequential_search(a_list,item):
        pos = 0
        found = False

        while pos < len(a_list) and not found:
                if a_list[pos] == item:
                        found = True
                else:
                        pos = pos + 1

        print("pos:%d"%pos)

        return found

def ordered_sequential_search(a_list,item):
        pos = 0
        found = False
        stop = False

        while pos < len(a_list) and not found and not stop:
                if a_list[pos] == item:
                        found = True
                else:
                        if a_list[pos] > item:
                                stop = True
                        else:
                                pos = pos + 1
        print("pos:%d" % pos)
        return found

test_list = [1,2,8,13,17,19,32,43,0]
test_lista = [15,18,2,19,18,0,8,14,19,14]
test_listb = [3,5,6,8,11,12,14,15,17,18]
print(sequential_search(test_lista,18))
print(sequential_search(test_lista,13))
print(ordered_sequential_search(test_list,3))
print(ordered_sequential_search(test_listb,13))

　　运算结果：

　　

pos:1
True
pos:10
False
pos:2
False
pos:6
False