DATA STRUCTURES • ALGORITHMS

Longest Subarray with Sum K

Find the length of the longest contiguous subarray that sums up to a given value K. This version uses the optimal two-pointer approach for non-negative numbers.

Time

O(N)

Space

O(1)

Key Principle 1

Sliding window (Two Pointers)

Key Principle 2

Expand 'right' to increase sum

Key Principle 3

Shrink 'left' if sum exceeds K

Key Principle 4

Track max length whenever sum equals K

LONGEST_K_LAB
Current Step
Goal: Find longest subarray with sum K=3. Starting with two pointers at index 0.
Max Length
0
Playback
Window Stats ⠿
Current Sum0
K Target3
Window Logic ⠿
1int left = 0, right = 0, sum = 0, maxLen = 0;
2while (right < n) {
3    sum += nums[right];
4    while (sum > k && left <= right) {
5        sum -= nums[left++];
6    }
7    if (sum == k) {
8        maxLen = Math.max(maxLen, right - left + 1);
9    }
10    right++;
11}
1
L
2
1
3
2
1
3
1
4
1
5
4
6
2
7
3
8
Current Window Sum
0
Max Length Found
0

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Longest Subarray K

Longest Subarray K

Longest Subarray with Sum K

Longest Subarray with Sum K