Leetcode 523. Continuous Subarray Sum Prefix 坑

Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise.

A good subarray is a subarray where:

its length is at least two, and

the sum of the elements of the subarray is a multiple of k.

Note that:

A subarray is a contiguous part of the array.

An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a multiple of k.

Example 1:

Input: nums = [23,2,4,6,7], k = 6

Output: true

Explanation: [2, 4] is a continuous subarray of size 2 whose elements sum up to 6.

Example 2:

Input: nums = [23,2,6,4,7], k = 6

Output: true

Explanation: [23, 2, 6, 4, 7] is an continuous subarray of size 5 whose elements sum up to 42.

42 is a multiple of 6 because 42 = 7 * 6 and 7 is an integer.

Example 3:

Input: nums = [23,2,6,4,7], k = 13

Output: false

Constraints:

1 <= nums.length <= 105

0 <= nums[i] <= 109

0 <= sum(nums[i]) <= 231 - 1

1 <= k <= 231 - 1


It's easy to come up with prefix array, but the potential bug is that the its length is at least two. The following code is finished after several attempts:

python 复制代码
class Solution:
    def checkSubarraySum(self, nums: List[int], k: int) -> bool:
        l = len(nums)
        if (l <= 1):
            return False
        prefix_dic = {0:-1} # take care 0 is with any prefix
        cur_sum = 0
        
        for i in range(l):
            cur_sum = (cur_sum+nums[i]) % k
            # take care the following conditions
            if cur_sum in prefix_dic and (i-prefix_dic[cur_sum] >= 2):
                return True
            if cur_sum not in prefix_dic:
                prefix_dic[cur_sum] = i
        return False
相关推荐
kessy1几秒前
安全与续航兼备的“国密芯”——LKT6810U
算法
leo__5207 分钟前
基于经验模态分解的去趋势波动分析(EMD-DFA)方法
人工智能·算法·机器学习
lzptouch29 分钟前
AdaBoost(Adaptive Boosting)算法
算法·集成学习·boosting
南方的狮子先生38 分钟前
【数据结构】(C++数据结构)查找算法与排序算法详解
数据结构·c++·学习·算法·排序算法·1024程序员节
前进的李工1 小时前
LeetCode hot100:560 和为k的子数组:快速统计法
python·算法·leetcode·前缀和·哈希表
学编程就要猛1 小时前
数据结构初阶:Java中的ArrayList
java·开发语言·数据结构
试试勇气1 小时前
算法工具箱之双指针
数据结构
在等晚安么2 小时前
力扣面试经典150题打卡
java·数据结构·算法·leetcode·面试·贪心算法
AndrewHZ2 小时前
【图像处理基石】图像滤镜的算法原理:从基础到进阶的技术解析
图像处理·python·opencv·算法·计算机视觉·滤镜·cv
lxmyzzs2 小时前
【图像算法 - 30】基于深度学习的PCB板缺陷检测系统: YOLOv11 + UI界面 + 数据集实现
人工智能·深度学习·算法·yolo·缺陷检测