数组中累加和小于等于k的最长子数组

问题描述：

给定一个无序数组arr，其中元素可正、可负、可0，给定一个整数 k。求arr所有的子数组中累加和小于或等于k的最长子数组长度。例如:arr=[3,-2,-4,0,6]，k=-2，相加和小于或等于-2的最长子数组为{3,-2,-4,0}，所以结果返回4。

代码如下：

int getLessIndex(int arr[], int len, int num)
{
    int low = 0;
    int high = len - 1;
    int mid = 0;
    int ret  = -1;

    while(low <= high)
    {
        mid = (low + high) / 2;
        if(arr[mid] >= num)
        {
            ret = mid;
            high = mid - 1;
        }
        else
        {
            low  = mid + 1;
        }
    }

    return ret;
}


int maxLength(int arr[], int len, int k)
{
    int *pSums = new int[len + 1];
    int sum = 0;
    pSums[0] = sum;

    for(int i = 0; i < len; ++i)
    {
        sum += arr[i];
        pSums[i + 1] = max(sum, pSums[i]);
    }

    sum = 0;
    int ret = 0;
    int idx = 0;
    int dis = 0;
    for(int i = 0; i < len; ++i)
    {
        sum += arr[i];
        idx = getLessIndex(pSums, len, sum - k);
        dis = (idx == -1 ? 0 : i - idx  + 1);
        ret = max(ret, dis);
    }
    
    delete[] pSums;
    return ret;
}