Daily Temperatures

LeetCode Q 739 - Daily Temperatures

Given a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.

For example, given the list of temperatures T = [73, 74, 75, 71, 69, 72, 76, 73], your output should be [1, 1, 4, 2, 1, 1, 0, 0].

Note: The length of temperatures will be in the range [1, 30000]. Each temperature will be an integer in the range [30, 100].

Solution

Code

public int[] dailyTemperatures(int[] T) {
  int[] res = new int[T.length];
  
  Deque<Integer> stack = new ArrayDeque<>(); // storing Ts in descending order from the end of the array to the front

  for (int i = T.length - 1; i >= 0; i--) {
    while (!stack.isEmpty() && T[stack.peek()] <= T[i]) 
      stack.pop();

    if (!stack.isEmpty()) res[i] = stack.peek() - i;
    
    stack.push(i);
  }

  return res;
}