LeetCode/java/continuous-subarrays.java

class Solution {
  private int i, j;
  private int runningMin, runningMax;

  private long subarraysInRange() {
    long length = j - i;
    return (length * (length + 1)) / 2;
  }

  private long check(int[] nums) {
    runningMin = Math.min(runningMin, nums[j]);
    runningMax = Math.max(runningMax, nums[j]);
    if (runningMax - runningMin <= 2) {
      // differences are satisfied, can continue
      return 0l;
    }

    long total = subarraysInRange();

    i = j;
    runningMin = runningMax = nums[j];

    while (i > 0 && Math.abs(nums[j] - nums[i - 1]) <= 2) {
      --i;
      runningMin = Math.min(runningMin, nums[i]);
      runningMax = Math.max(runningMax, nums[i]);
    }

    // subtract duplicitous count
    if (i < j) {
      total -= subarraysInRange();
    }

    return total;
  }

  public long continuousSubarrays(int[] nums) {
    long total = 0;

    i = 0;
    runningMin = runningMax = nums[i];
    for (j = 0; j < nums.length; ++j) {
      total += check(nums);
    }

    // count final subarrays
    total += subarraysInRange();

    return total;
  }
}