仅将两个字符串中常见的字母转换为大写？

Question

假设str1=“Apple”和str2=“pen”。现在比较str1和str2，找出常见的字母。然后用普通大写字母打印str1。怎么做？

输出：

"aPPlE"

Answer 1

String s1 = "Apple";
String s2 = "pen";
HashSet<Character> set = new HashSet();
for(char c: s1.toCharArray()) {
   if(set.contains(c)) {
       continue;
} else if(s2.indexOf(c) >=0 ) {
       set.add(c);
   }
}
StringBuilder sb = new StringBuilder();
for(char c: s1.toCharArray()) {
   if(set.contains(c)) {
       sb.append(Character.toUpperCase(c));
   } else {
      sb.append(c);
   } 
}
System.out.println(sb.toString());

Answer 2

str1 = "Apple"
str2 = "pen"

# make sure not other letters are in uppercase
str1 = str1.lower()
str2 = str2.lower()

for c in str1:
    if c in str2:
        str1 = str1.replace(c, c.upper())
print(str1)

输出