面试题：数组中2个数的和

给定 nums = [2, 7, 11, 15], target = 9
因为 nums[0] + nums[1] = 2 + 7 = 9
所以返回 [0, 1]

def twosum(array,target):
    # 先判断边界条件
    if len(array)<=1:
        return None
    # 正常遍历
    for i in range(len(array)):
        res = target-array[i]
        if res in array:
            idxs = array.index(res)
            return [i,idxs]
    return None 

if __name__ == "__main__":
    array=[2, 7, 11, 15]
    target = 9
    print(twosum(array,target))