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].

class Solution {
    public int[] dailyTemperatures(int[] temperatures) {
        Stack<Integer> stack = new Stack<>();
        int[] ret = new int[temperatures.length];
        for(int i = 0; i < temperatures.length; i++) {
            while(!stack.isEmpty() && temperatures[i] > temperatures[stack.peek()]) {
                int idx = stack.pop();
                ret[idx] = i - idx;
            }
            stack.push(i);
        }
        return ret;
    }
}