array score（C++數組得分）

解題思路：

（1）求得初始窗口的值，最後使用進一個出一個的方法，滑動求值

class Solution {
public:
    /**
     * @param nums: the array to be scored.
     * @param k: the requirement of subarray length.
     * @param u: if the sum is less than u, get 1 score.
     * @param l: if the sum is greater than l, lose 1 score.
     * @return: return the sum of scores for every subarray whose length is k.
     */
    int arrayScore(vector<int> &nums, int k, long long u, long long l) {
        int score = 0;
        long long sum = 0;
        for(int i=0;i<k;i++) sum+=nums[i];
        if(sum<u) score++;
        else if(sum>l) score--;
        for(int i=k;i<nums.size();i++) {
            sum = sum+nums[i]-nums[i-k];
            if(sum<u) score++;
            else if(sum>l) score--;
        }
        return score;
    }
};