795.区间子数组个数

class Solution {
    public int numSubarrayBoundedMax(int[] nums, int left, int right) {
        return lessEqualsThan(nums,right) - lessEqualsThan(nums,left - 1);
    }
    private int lessEqualsThan(int[] nums,int k){
        int len = nums.length;
        int res = 0,left = 0,right = 0;
        //循环不变量：nums[left,right]里的所有元素都小于等于k
        while( right < len){
            if(nums[right] > k){
                left = right + 1;
            }
            res += right - left;
            right++;
        }
        return res;
    }
}