13ms Java solution with explanation

• ``````public static int[] dailyTemperatures(int temperatures[]) {
int n = temperatures.length;
if (n == 0)
return temperatures;

// Values at an index are the number of days until a warmer temperature,
// for the corresponding temperature at temperatures[index].
int days[] = new int[n];

// Last day has no warmer days after it.
days[n - 1] = 0;

// For all days except last, iterate through starting at end of array.
// Won't run if n == 1, taken care of above.
int tempIndex;
for (int index = n - 2; index >= 0; index--) {

// Check if the next day is warmer.
if (temperatures[index] < temperatures[index + 1]) {
days[index] = 1;
continue;
}

// If this code isn't continued over, then the next day is not warmer than the
// day at index, so therefore the next day that could possibly be warmer is at
// the day that is warmer than the next day.
tempIndex = index + 1 + days[index + 1];

/*
* Move tempIndex to the index of the temperature that is the next warm day.
*
* Loop runs while a warmer day hasn't been found, move tempIndex to the next
* possible warmer day, based on property that the next possible warmer day is
* at the next day's (given that the next day is not warmer than this day)
* warmer day. If the next day does not have a warmer day (days[tempIndex] ==
* 0), then this day cannot have a warmer day.
*
* Problem: The loop exits when the next warmer day is found and when no options
* are confirmed. Clarify this in assignment after the while loop by ensuring that
* the temperature at tempIndex is indeed warmer than the temperature at index.
*/
while (temperatures[index] >= temperatures[tempIndex] && days[tempIndex] > 0)
tempIndex += days[tempIndex]; // Move tempIndex to next possibly warmer day.

if (temperatures[index] < temperatures[tempIndex])
days[index] = tempIndex - index;
else
days[index] = 0;
}

return days;
}
``````

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