无重复字符的最长子串

// Problem: Find the length of the longest substring without repeating characters
// Approach: Java Streams are not the best fit for this problem due to its stateful nature, but we can simulate the sliding window approach using Streams in combination with additional state tracking.
// This solution is provided for completeness but is less efficient than using traditional loops.
 
import java.util.*;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
 
public class StreamSolution {
    public int lengthOfLongestSubstring(String s) {
        Map<Character, Integer> map = new HashMap<>();
        BiFunction<Character, Integer, Integer> updateMap = (c, index) -> {
            map.put(c, index);
            return index;
        };
        int[] result = new int[1];
        IntStream.range(0, s.length())
            .boxed()
            .collect(Collectors.toMap(i -> s.charAt(i), Function.identity(), (a, b) -> b, () -> map))
            .forEach((c, i) -> {
                if (map.get(c) != null && map.get(c) >= result[0]) {
                    result[0] = map.get(c) + 1;
                }
                map.put(c, i);
                result[0] = Math.max(result[0], i - result[0] + 1);
            });
        return result[0];
    }
}