Leetcode 739 - Daily Temperatures

Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait after the ith day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0 instead.

Example 1:

Input: temperatures = [73,74,75,71,69,72,76,73]
Output: [1,1,4,2,1,1,0,0]

Example 2:

Input: temperatures = [30,40,50,60]
Output: [1,1,1,0]

Example 3:

Input: temperatures = [30,60,90]
Output: [1,1,0]

Constraints:

• 1 <= temperatures.length <= 105

• 30 <= temperatures[i] <= 100

Solution

On this question, the simple solution is to create a stack of array to keep track of the value and the index and add them to the stack after removing the lesser elements from the stack and calculating the index between them

to keep track of the next element, we will have an array to store the difference -

int[] res = new int[temperatures.length];

Then finally return the result array

class Solution {
    public int[] dailyTemperatures(int[] temperatures) {
        if(temperatures.length == 0) return new int[] {-1, -1};
        Stack<int[]> stack = new Stack<>();
        int[] res = new int[temperatures.length];
        for(int i=0; i < temperatures.length; i++) {
            while(!stack.isEmpty() && stack.peek()[0] < temperatures[i]){
                int[] temp = stack.pop();
                res[temp[1]] = i - temp[1];
            }
            stack.push(new int[]{temperatures[i], i});
        }
        return res;
    }
}