32. Daily Temperatures

class Solution:
    def dailyTemperatures(self, temperatures: List[int]) -> List[int]:
        res = [0] * len(temperatures)
        stack = []                       # indices of days still waiting, temps decreasing
        for i, t in enumerate(temperatures):
            while stack and temperatures[stack[-1]] < t:
                j = stack.pop()          # day j finally found a warmer day
                res[j] = i - j
            stack.append(i)
        return res

class Solution {
    public int[] dailyTemperatures(int[] temperatures) {
        int[] res = new int[temperatures.length];
        Deque<Integer> stack = new ArrayDeque<>();   // indices waiting for a warmer day
        for (int i = 0; i < temperatures.length; i++) {
            while (!stack.isEmpty() && temperatures[stack.peek()] < temperatures[i]) {
                int j = stack.pop();
                res[j] = i - j;
            }
            stack.push(i);
        }
        return res;
    }
}

class Solution {
public:
    vector<int> dailyTemperatures(vector<int>& temperatures) {
        vector<int> res(temperatures.size(), 0), st;   // st: indices waiting for a warmer day
        for (int i = 0; i < (int)temperatures.size(); i++) {
            while (!st.empty() && temperatures[st.back()] < temperatures[i]) {
                res[st.back()] = i - st.back();
                st.pop_back();
            }
            st.push_back(i);
        }
        return res;
    }
};

function dailyTemperatures(temperatures) {
  const res = new Array(temperatures.length).fill(0), stack = []; // indices waiting for a warmer day
  for (let i = 0; i < temperatures.length; i++) {
    while (stack.length && temperatures[stack[stack.length - 1]] < temperatures[i]) {
      const j = stack.pop();
      res[j] = i - j;
    }
    stack.push(i);
  }
  return res;
}