leetcode739. 每日温度

// 暴力法
class Solution {
     
    public int[] dailyTemperatures(int[] T) {
     
        int len = T.length;
        int[] result = new int[len];

        for (int i = 0; i < len; i++) {
     
            for (int j = i + 1; j < len; j++) {
     
                if (T[i] < T[j]) {
     
                    result[i] = j - i;
                    break;
                }
            }
        }
        return result;
    }
}

// 暴力法优化
// 先从计算右边，那么我们计算过的位置就不需要重复计算
class Solution {
     
    public int[] dailyTemperatures(int[] T) {
     
        int len = T.length;
        int[] result = new int[len];

        //从右向左遍历
        for (int i = len - 2; i >= 0; i--) {
     
            // j+= result[j]是利用已经有的结果进行跳跃
            for (int j = i + 1; j < len; j += result[j]) {
     
                if (T[j] > T[i]) {
     
                    result[i] = j - i;
                    break;
                }
                //遇到0表示后面不会有更大的值，那当然当前值就应该也为0
                else if (result[j] == 0) {
     
                    result[i] = 0;
                    break;
                }
            }
        }
        return result;
    }
}

// 栈
class Solution {
     
    public int[] dailyTemperatures(int[] T) {
     
        Stack<Integer> stack = new Stack<>();
        int len = T.length;
        int[] result = new int[len];
        for (int i = 0; i < len; i++) {
     
            while (!stack.isEmpty() && T[i] > T[stack.peek()]) {
     
                result[stack.peek()] = i - stack.peek();
                stack.pop();
            }
            stack.push(i);
        }
        return result;
    }
}