剑指offer基础版 ---- 第27天

class Solution {
    
    public int[] maxSlidingWindow(int[] nums, int k) {
    
        if(nums.length == 0 || k == 0) return new int[0];
        Deque<Integer> deque = new LinkedList<>();
        int[] res = new int[nums.length - k + 1];
        for(int j = 0, i = 1 - k; j < nums.length; i++, j++) {
    
            // 删除 deque 中对应的 nums[i-1]
            if(i > 0 && deque.peekFirst() == nums[i - 1])
                deque.removeFirst();
            // 保持 deque 递减
            while(!deque.isEmpty() && deque.peekLast() < nums[j])
                deque.removeLast();
            deque.addLast(nums[j]);
            // 记录窗口最大值
            if(i >= 0)
                res[i] = deque.peekFirst();
        }
        return res;
    }
}

class MaxQueue {
    
    int[] q = new int[20000];
    int begin = 0, end = 0;

    public MaxQueue() {
    

    }
    
    public int max_value() {
    
        int ans = -1;
        for (int i = begin; i != end; ++i) {
    
            ans = Math.max(ans, q[i]);
        }
        return ans;
    }
    
    public void push_back(int value) {
    
        q[end++] = value;
    }
    
    public int pop_front() {
    
        if (begin == end) {
    
            return -1;
        }
        return q[begin++];
    }
}

/**
 * Your MaxQueue object will be instantiated and called as such:
 * MaxQueue obj = new MaxQueue();
 * int param_1 = obj.max_value();
 * obj.push_back(value);
 * int param_3 = obj.pop_front();
 */