Super Simple Sliding Window Count Java(O(n*n))
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n1. find a window where 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n1. find a window where any freq>=k and add all the window from that point to n-1(n-r)\n# Complexity\n- Time complexity:O(n*n)\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:O(26)\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```java []\nclass Solution {\n    public int numberOfSubstrings(String s, int k) {\n        int count = 0;\n        int n = s.length();\n        for (int l = 0; l < n; l++) {\n            int[] freq = new int[26];\n            for (int r = l; r < n; r++) {\n                char c = s.charAt(r);\n                freq[c - \'a\']++;\n                if (freq[c - \'a\'] >= k) {\n                    count += (n - r);\n                    break;\n                }\n            }\n        }\n        return count;\n    }\n}\n```
['Java']