算法集锦

1.二分查找（折半查找）

def binary_search(li,val):
    left = 0
    right = len(li)-1  # 表示索引
    while left <= right:
        mid = int((left + right)/2)
        if val == li[mid]:
            return mid  # 返回索引
        elif val < li[mid]:
            right = mid-1
        elif val > li[mid]:
            left = mid + 1
    else:
        return None

li = [1,2,3,4,5,6,7,8,9]
print(binary_search(li, 9))

输出结果：8