Continuous Subarray Sum


#1

Given a list of non-negative numbers and a target integer k, write a function to check if the array has a continuous subarray of size at least 2 that sums up to the multiple of k, that is, sums up to n*k where n is also an integer.

Example 1:

Input: [23, 2, 4, 6, 7],  k=6
Output: True
Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.

Example 2:

Input: [23, 2, 6, 4, 7],  k=6
Output: True
Explanation: Because [23, 2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.

Note:

  1. The length of the array won't exceed 10,000.
  2. You may assume the sum of all the numbers is in the range of a signed 32-bit integer.

#2

The below program uses a map to store the remainders at each index sum.

func checkSubarraySum(nums []int, k int) bool {
    m := make(map[int]int, 0)
    m[0] = -1
    runningSum := 0
    for i:=0;i<len(nums);i++{
        runningSum += nums[i]
        if k!=0{
            runningSum %= k
        }
        if val, ok := m[runningSum]; ok{
            if i-val > 1{ return true}
        }else {
            m[runningSum] = i
        }
    }
    return false
}