try to publish result
rust []\nimpl Solution {\n    pub fn length_after_transformations(s: String, t: i32) -> i32 {\n        let module = 10_i32.pow(9) + 7;\n        // use a hashmap
```rust []\nimpl Solution {\n    pub fn length_after_transformations(s: String, t: i32) -> i32 {\n        let module = 10_i32.pow(9) + 7;\n        // use a hashmap to update the frequency of each letter\n        let mut frequency_map: std::collections::HashMap<char, i32> = (\'a\'..=\'z\').map(|c| (c, 0)).collect();\n        for ch in s.chars() {\n            *frequency_map.get_mut(&ch).unwrap() += 1;\n        }\n        for _ in 0..t {\n            // step 1: remember the frequency of z, as it will be overwritten later\n            let z_freq = *frequency_map.get(&\'z\').unwrap() % module;\n            // step 2: update each non-z character from y to b\n            for ch in (\'a\'..=\'y\').rev() {\n                let ch_freq = frequency_map.get(&ch).unwrap();\n                let next_ch = (ch as u8 + 1) as char;\n                *frequency_map.get_mut(&next_ch).unwrap() = *ch_freq;\n            }\n            // step 3: transform \'z\'\n            *frequency_map.get_mut(&\'a\').unwrap() = z_freq;\n            // avoid add overflow\n            let tmp = *frequency_map.get(&\'b\').unwrap() % module;\n            *frequency_map.get_mut(&\'b\').unwrap() = (tmp + z_freq) % module;\n        }\n        frequency_map.values().fold(0_i32, |acc, &x| (acc + x) % module)\n    }\n}\n\n```
['Rust']