for my programm I want to fill a vector with arrays containing integers, but at some point I might want to manipulate the last entry in the vector if present. I aim to perform this efficiently as possible. So I thought to do it in the following way. I tried to change the code and get it working, but I failed so far. I hope someone can help me, so I provided a minimum example I work on to understand the issue.

for my programm I want to fill a vector with arrays containing integers, but at some point I might want to manipulate the last entry in the vector if present. I aim to perform this efficiently as possible. So I thought to do it in the following way. I tried to change the code and get it working, but I failed so far. I hope someone can help me, so I provided a minimum example I work on to understand the issue.

I am a newbie in Rust. I want to iterate through a vector of String and modify the values. How will one do it? Below is the code I wrote, but it fails.