题解 | #牛牛的数列#

双向dp

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums intvector 
     * @return int
     */
    int maxSubArrayLength(vector<int>& nums) {
        // write code here
//         [7,2,3,1,5,6]
//          1 1 2 1 2 3
//          1 2 1 3 2 1

        int m = nums.size();
        if (m < 3) {
            return m;
        }
        vector<int> left(m, 1), right(m, 1);

        for (int i = 1; i < m; i++) {
            if (nums[i] > nums[i - 1]) {
                left[i] = left[i - 1] + 1;
            } 
        }
        for (int i = m - 2; i >= 0; i--) {
            if (nums[i] < nums[i + 1]) {
                right[i] = right[i + 1] + 1;
            }
        }
        int ans = 1;
        for (int i = 1; i < m - 1; i++) {
            if (nums[i + 1] - nums[i - 1] > 1) {
                ans = max(ans, left[i - 1] + right[i + 1] + 1);
            }
        }
        return ans;
    }
};