739. Daily Temperatures
Given a list of daily temperatures T, return a list such that, for each day in the input, tells you how many days you would have to wait until a warmer temperature. If there is no future day for which this is possible, put 0 instead.
For example, given the list of temperatures T = [73, 74, 75, 71, 69, 72, 76, 73], your output should be [1, 1, 4, 2, 1, 1, 0, 0].
Note: The length of temperatures will be in the range [1, 30000]. Each temperature will be an integer in the range [30, 100].
题意：这道题给一个 int 数组来代表当天的温度。 问最近比当下暖的一天是几天后？ 转化一下，这道题就是求最近比自己大的数。 单调栈的经典题呃。
代码
class Solution {
public int[] dailyTemperatures(int[] T) {
if(T == null || T.length == 0) return T;
Stack<Integer> stack = new Stack<>();
stack.push(0);
int[] ret = new int[T.length];
int i = 1;
while(i < T.length) {
while(!stack.isEmpty()&& T[i] > T[stack.peek()]) {
int index = stack.pop();
ret[index] = i - index;
}
stack.push(i);
i++;
}
while(!stack.isEmpty()) {
int index = stack.pop();
ret[index] = 0;
}
return ret;
}
}