2461. 长度为 K 子数组中的最大和

C代码：滑动窗口

long long maximumSubarraySum(int* nums, int numsSize, int k){
    int hash[100001] = {0};
    long long sum = 0;
    int l = 0;
    long long ans = 0;
    for (int r = 0; r < numsSize; ++r) {
        hash[nums[r]]++;
        sum += nums[r];
        while ((hash[nums[r]] >= 2) || (r - l + 1 > k)) {
            hash[nums[l]]--;
            sum -= nums[l];
            ++l;
        }
        if (r - l + 1 == k) {
            ans = fmax(ans, sum);
        }
    }
    return ans;
}