Minimum Size Subarray Sum

Try It Yourself

Use the editor below to find the shortest contiguous window whose sum reaches the target. The positive input values allow the window to shrink safely whenever its sum is large enough.

Submit your implementation when it passes the examples. Return zero if no window reaches the target.

Solution

Expand the right edge and add each value to the running sum. Whenever the sum reaches the target, record the current length and repeatedly remove values from the left to search for a shorter valid window.

If no valid length was recorded, return zero.

function minSubArrayLen(target, nums) {
  let left = 0;
  let sum = 0;
  let shortest = Infinity;

  for (let right = 0; right < nums.length; right++) {
    sum += nums[right];

    while (sum >= target) {
      shortest = Math.min(shortest, right - left + 1);
      sum -= nums[left];
      left++;
    }
  }

  return shortest === Infinity ? 0 : shortest;
}

Big O notation