替换字符后匹配

/* 
 * 思路: 
 * 1. 使用 Java Stream 构建从 old 到 new 的映射表。 
 * 2. 生成所有可能的 sub 替换形式。 
 * 3. 过滤出在 s 中的子串。 
 */ 
import java.util.*; 
import java.util.stream.*; 
public class Solution { 
    public boolean canTransform(String s, String sub, char[][] mappings) { 
        // 构建映射表 
        Map<Character, List<Character>> map = Arrays.stream(mappings) 
                .collect(Collectors.groupingBy(m -> m[0], 
                        Collectors.mapping(m -> m[1], Collectors.toList()))); 
        // 生成所有可能的字符串 
        return generateAll(sub.toCharArray(), map, 0).stream() 
                .anyMatch(s::contains); 
    } 
    private List<String> generateAll(char[] sub, Map<Character, List<Character>> map, int index) { 
        if (index == sub.length) { 
            return Collections.singletonList(new String(sub)); 
        } 
        List<String> results = new ArrayList<>(); 
        char original = sub[index]; 
        results.addAll(generateAll(sub, map, index + 1)); 
        if (map.containsKey(original)) { 
            for (char replacement : map.get(original)) { 
                sub[index] = replacement; 
                results.addAll(generateAll(sub, map, index + 1)); 
                sub[index] = original; 
            } 
        } 
        return results; 
    } 
}