use std::collections::HashMap;
fn longest_substring(s: &str) -> String {
let mut start = 0;
let mut max_length = 0;
let mut longest_substr = String::new();
let mut char_index_map = HashMap::new();
for (end, ch) in s.chars().enumerate() {
if let Some(&index) = char_index_map.get(&ch) {
if index >= start {
start = index + 1; // Move the start pointer to avoid duplicates
}
}
char_index_map.insert(ch, end); // Update the character's latest index
let current_length = end - start + 1;
if current_length > max_length {
max_length = current_length;
longest_substr = s[start..=end].to_string(); // Update the longest substring
}
}
longest_substr
}
fn main() {
// Test cases
println!("{}", longest_substring("abcabcbb")); // Output: "abc"
println!("{}", longest_substring("bbbbb")); // Output: "b"
println!("{}", longest_substring("xwwwqfwwxqwyq")); // Output: "xqwy"
}
/*
run:
abc
b
xqwy
*/
