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].
  • Simple problem

// find the first larger element with larger index
// monotonic stack
public int[] dailyTemperaturesMonotonicStack(int[] T) {
    Stack<Integer> stack = new Stack<>();
    // stack.push(Integer.MAX_VALUE);
    int[] result = new int[T.length];
    for(int i = 0; i < T.length; i++) {
        while(!stack.isEmpty() && T[stack.peek()] < T[i]) {
            int prev = stack.pop();
            result[prev] = i - prev;
        }
        stack.push(i);
    }
    return result;
}