update on 2 min read
String vs StringBuilder vs Span
Problem statement
During a recent interview, I was presented with a problem statement involving the use of the ’#’ symbol. The interviewer explained that this symbol should function as a backspace, and they requested me to devise a logical solution for resolving this scenario
Code
1: INPUT ==> abc#def# OUTPUT==> abcdef 2: INPUT ==> abc##def## OUTPUT==> adSolution 1:
first Solution I write this,
public string RemoveLastCharWithString(String word) { string result = ""; for (int i = 0; i < word.Length; i++) { if (word[i] != ' ' && word[i] == '#') { result = result.Remove(result.Length - 1, 1); } else if (word[i] != '#') { result += word[i]; } } return result; }Solution 2:
I forced to be changed as stringbuilder
public string RemoveLastCharWithStringBuilder(string word ) { StringBuilder result = new StringBuilder();
for (int i = 0; i < word.Length; i++) { if (word[i] != ' ' && word[i] == '#') { if (result.Length > 0) { result.Remove(result.Length - 1, 1); } } else if (word[i] != '#') { result.Append(word[i]); } } return result.ToString(); }Solution 3:
Then I realised we have other option and its optimized way to do .
public string RemoveLastCharWithSpan(String word) { Span<char> buffer = stackalloc char[word.Length]; int position = 0;
foreach (char c in word) { if (c == '#' && position > 0) { position--; } else if (c != '#') { buffer[position++] = c; } }
return new string(buffer.Slice(0, position)); }Benchmark Results
The metrix in below shows the results of our performance benchmarks.
| Method | Mean | Error | StdDev | Min | Max | Gen0 | Allocated ||-------------------------------- |---------:|---------:|---------:|---------:|---------:|-------:|----------:|| RemoveLastCharWithString | 53.36 ns | 0.873 ns | 1.104 ns | 52.04 ns | 56.01 ns | 0.0497 | 416 B || RemoveLastCharWithStringBuilder | 22.77 ns | 0.251 ns | 0.209 ns | 22.59 ns | 23.34 ns | 0.0172 | 144 B || RemoveLastCharWithSpan | 12.08 ns | 0.271 ns | 0.489 ns | 11.38 ns | 12.98 ns | 0.0048 | 40 B |Note: I will add separate article to show ” How to add BenchMarck in Dotnet ?”
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