通过遍历而非排序求最值 python list in 时间复杂度 列表元素存在性

Write a function:

def solution(A)

that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.

For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.

Given A = [1, 2, 3], the function should return 4.

Given A = [−1, −3], the function should return 1.

Write an efficient algorithm for the following assumptions:

• N is an integer within the range [1..100,000];
• each element of array A is an integer within the range [−1,000,000..1,000,000].

def solution(A):
    ret = 1
    c = len(A)
    for i in range(0, c, 1):
        if A[i] <= 0:
            continue
        if ret not in A:
            return ret
        else:
            ret += 1
    return ret




python list in  时间复杂度 列表元素存在性