523. Continuous Subarray Sum.md

523. Continuous Subarray Sum

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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 a 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:

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

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Solution

• mine

  • Java

    ``

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• the most votes

  Runtime: 2 ms, faster than 99.74%,Memory Usage: 39.7 MB, less than 88.24% of Java online submissions

  public boolean checkSubarraySum(int[] nums, int k) {
      Map<Integer, Integer> map = new HashMap<>();
      map.put(0,-1);
      int runningSum = 0;
      for (int i=0;i<nums.length;i++) {
          runningSum += nums[i];
          if (k != 0) runningSum %= k; 
          Integer prev = map.get(runningSum);
          if (prev != null) {
              if (i - prev > 1) return true;
          }
          else map.put(runningSum, i);
      }
      return false;
  }