Daily Temperatures

Try It Yourself

Use the editor below to calculate how many days each temperature waits for a warmer value. Store indices whose answer has not yet been found.

Submit your implementation when it passes the examples. Equal temperatures are not warmer, and some days may never receive an answer.

Solution

Keep a stack of unresolved indices whose temperatures decrease from bottom to top. A new warmer temperature resolves every cooler index at the top.

Pop each resolved index and store the distance to the current day. Indices left in the stack keep the default answer of zero.

function dailyTemperatures(temperatures) {
  const answer = Array(temperatures.length).fill(0);
  const stack = [];

  for (let day = 0; day < temperatures.length; day++) {
    while (
      stack.length > 0 &&
      temperatures[day] > temperatures[stack[stack.length - 1]]
    ) {
      const previousDay = stack.pop();
      answer[previousDay] = day - previousDay;
    }

    stack.push(day);
  }

  return answer;
}

Big O notation