LeetCode 325: Maximum Size Subarray Sum Equals k

LeetCode 325 Solution Explanation

Explanation:

To solve this problem, we can use a hashmap to store the cumulative sum up to each index. We iterate through the array keeping track of the cumulative sum and store it in the hashmap along with its index. At each index, we check if the current sum minus the target k exists in the hashmap. If it does, we update the maximum length of the subarray. We return the maximum length of the subarray that sums to k.

Algorithm:

  1. Initialize a hashmap to store cumulative sums and their corresponding indices.
  2. Initialize variables maxLen to store the maximum length of the subarray and sum to store the cumulative sum.
  3. Iterate through the array:
    • Update sum with the current element.
    • If sum - k is present in the hashmap, update maxLen if necessary.
    • If sum is not present in the hashmap, store it with its index.
  4. Return maxLen.

Time Complexity: O(n) - We iterate through the array once. Space Complexity: O(n) - We use a hashmap to store cumulative sums.

:

LeetCode 325 Solutions in Java, C++, Python

class Solution {
    public int maxSubArrayLen(int[] nums, int k) {
        Map<Integer, Integer> map = new HashMap<>();
        int maxLen = 0;
        int sum = 0;
        
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (sum == k) {
                maxLen = i + 1;
            } else if (map.containsKey(sum - k)) {
                maxLen = Math.max(maxLen, i - map.get(sum - k));
            }
            if (!map.containsKey(sum)) {
                map.put(sum, i);
            }
        }
        
        return maxLen;
    }
}

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