739. Daily temperature (medium)

Ideas:

Observe the example given:

Given a list  temperatures = [73, 74, 75, 71, 69, 72, 76, 73] , the output should be  [1, 1, 4, 2, 1, 1, 0, 0]

Traverse from the front to the back, if the temperature is greater than the previous one, pop the previous one, save the current subscript-the value of the previous value subscript, and finally save the current subscript into the stack. Obviously, the monotonic stack is used

 

class Solution {
    public int[] dailyTemperatures(int[] T) {
		int n=T.length;
		Deque<Integer> stack=new ArrayDeque<>();
		int[] ans=new int[n];
		
		for(int i=0;i<n;i++){
                        //注意：存入stack的是下标
			while(!stack.isEmpty()&&T[i]>T[stack.peekLast()]){
				int j=stack.removeLast();
				ans[j]=i-j;
			}

			//要在把所有<temp的温度弹出后才能把temp压入栈中
			//还包含了一层意思，如果不满足while的条件，也就是
			//temp<stack.peek()也压入栈中
			stack.addLast(i);
		}
		
		return ans;
	}
}