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523. Continuous Subarray Sum

Given an integer array nums and an integer k, return trueifnumshas a good subarray orfalseotherwise.

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

Solutions (Rust)

1. Solution

use std::collections::HashMap;implSolution{pubfncheck_subarray_sum(nums:Vec<i32>,k:i32) -> bool{letmut prefix_mod = 0;letmut mod_indices = HashMap::from([(0, -1)]);for i in0..nums.len(){ prefix_mod = (prefix_mod + nums[i]) % k;match mod_indices.get(&prefix_mod){Some(j)if j + 1 < i asi32 => returntrue,None => { mod_indices.insert(prefix_mod, i asi32);} _ => (),}}false}}