Understandable approach.
Intuition\n Describe your first thoughts on how to solve this problem. \n\n# Approach\n Describe your approach to solving the problem. \n\n# Complexity\n- Time 
# Intuition\n<!-- Describe your first thoughts on how to solve this problem. -->\n\n# Approach\n<!-- Describe your approach to solving the problem. -->\n\n# Complexity\n- Time complexity:\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity:\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```cpp []\nclass Solution {\npublic:\n    long long mod=1e9+7;\n\n    long long dp[100001][26];\n\n    long long trans(int ch,int level,int t){\n        if(level==t)\n        {\n            return 1;\n        }\n        int ans=0;\n        if(dp[level][ch]!=-1)\n        {\n            return dp[level][ch];\n        }\n        if(ch==25)\n        {\n            ans=(trans(0,level+1,t)%mod+trans(1,level+1,t)%mod)%mod;\n        }\n        else\n        {\n            return trans(ch+1,level+1,t)%mod;\n        }\n        return dp[level][ch]=ans;\n    }\n\n    int lengthAfterTransformations(string s, int t) {\n        memset(dp,-1,sizeof(dp));\n        long long ans=0;\n        unordered_map<char,long long> m;\n        for(auto i:s)\n            {\n                m[i]++;\n            }\n        for(int i=0;i<26;i++)\n            {\n                char c=\'a\'+i;\n                if(m[c]>0)\n                {\n                    int rec=trans(i,0,t);\n                    ans= (ans%mod + (m[c]%mod * rec%mod)%mod)%mod;\n                }\n            }\n        return ans;\n    }\n};\n```
['C++']