Daily Temperatures LeetCode solution in Java

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class Solution {
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  public int[] dailyTemperatures(int[] temperatures) {
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    HashMap<Integer, Integer> hm = new HashMap<>();
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    Stack<Integer> st = new Stack<>();
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    for (int i = 0; i < temperatures.length; i++) {
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      while (st.size() > 0 && temperatures[i] > temperatures[st.peek()]) {
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        hm.put(st.pop(), i);
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      }
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      st.push(i);
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    }
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    int[] ans = new int[temperatures.length];
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    for (int i = 0; i < temperatures.length; i++) {
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      if (hm.containsKey(i)) {
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        ans[i] = hm.get(i) - i;
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      } else {
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        ans[i] = 0;
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      }
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    }
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    return ans;
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  }
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}