HackerRank - Counting Valleys

Problem

An avid hiker keeps meticulous records of their hikes. During the last hike that took exactly  steps, for every step it was noted if it was an uphill, , or a downhill,  step. Hikes always start and end at sea level, and each step up or down represents a  unit change in altitude. We define the following terms:

• A mountain is a sequence of consecutive steps above sea level, starting with a step up from sea level and ending with a step down to sea level.
• A valley is a sequence of consecutive steps below sea level, starting with a step down from sea level and ending with a step up to sea level.

Given the sequence of up and down steps during a hike, find and print the number of valleys walked through.

Constraints

• $2 \leq steps \leq 10^6$
• $path[i] \in {U D}$

🙋‍♂️ Solution

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function countingValleys(n, path) {
  // Write your code here
  let isInValley = false;
  let valleyCount = 0;
  let currentAltitude = 0;
  const steps = path.split("");

  steps.map((step) => {
    if (step === "D") currentAltitude--;
    if (step === "U") currentAltitude++;

    if (currentAltitude < 0 && !isInValley) {
      isInValley = true;
      valleyCount++;
    }
    if (currentAltitude >= 0) {
      isInValley = false;
    }
  });

  return valleyCount;
}

• 현재 고도가 0보다 낮고, 협곡에 처음 들어갔을 때만 valleyCount 를 + 1 한다.
• 현재 고도가 0보다 같거나 크면 isInValley 를 false 로 바꾼다.

👀 Other Solution

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function countingValleys(n, s) {
  let steps = s.split("");
  let valleyCount = 0;
  let currentSeaLevel = 0;
  let valleyStatus = false;
  steps.forEach((step) => {
    step === "U" ? currentSeaLevel++ : currentSeaLevel--;
    if (currentSeaLevel < 0 && !valleyStatus) {
      valleyCount++;
      valleyStatus = true;
    } else if (currentLevel >= 0 && valleyStatus) {
      valleyStatus = false;
    }
  });
  return valleyCount;
}

• 풀이는 비슷하지만, 변수명을 이해하기 쉽게 짓는 방법을 참고했다.