30-Maximum-Size-Subarray-Sum-Equals-K.md

Maximum Size Subarray Sum Equals K

Problem Link

https://leetcode.com/problems/maximum-size-subarray-sum-equals-k/

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Pattern

• Prefix Sum
• Hash Table

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Approach

Use HashMap to track first occurrence of each prefix sum; max length where sum = k.

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Time Complexity

O(n)

Space Complexity

O(n)

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Java Solution

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