For further help with Coding Bat (Java), please check out my books. I am also available for tutoring.
countPairs:
public int countPairs(String str) {
if (str.length() < 3) return 0;
if (str.charAt(0) == str.charAt(2))
return 1 + countPairs(str.substring(1));
return countPairs(str.substring(1));
}
countAbc:
public int countAbc(String str) {
if (str.length() < 3) return 0;
if (str.substring(0, 3).equals("abc")
|| str.substring(0, 3).equals("aba"))
return 1 + countAbc(str.substring(1));
return countAbc(str.substring(1));
}
count11:
public int count11(String str) {
if (str.length() < 2) return 0;
if (str.substring(0, 2).equals("11"))
return 1 + count11(str.substring(2));
return count11(str.substring(1));
}
stringClean:
public String stringClean(String str) {
if (str.length() < 2) return str;
if (str.charAt(0) == str.charAt(1))
return stringClean(str.substring(1));
return str.charAt(0) + stringClean(str.substring(1));
}
countHi2:
public int countHi2(String str) {
if (str.length() < 2) return 0;
if (str.substring(0, 2).equals("hi"))
return 1 + countHi2(str.substring(2));
if (str.charAt(0) == 'x' && str.length() >= 3) {
if (str.substring(1, 3).equals("hi"))
return countHi2(str.substring(3));
return countHi2(str.substring(1));
}
return countHi2(str.substring(1));
}
parenBit:
public String parenBit(String str) {
if (!str.substring(0, 1).equals("("))
return parenBit(str.substring(1));
return (str.substring(0, str.indexOf(")") + 1));
}
nestParen:
public boolean nestParen(String str) {
if (str.equals("") || str.equals("()")) return true;
if (str.charAt(0) == '(' && str.charAt(str.length() - 1) == ')')
return nestParen(str.substring(1, str.length() - 1));
return false;
}
strCount:
public int strCount(String str, String sub) {
if (str.length() < sub.length()) return 0;
if (str.substring(0, sub.length()).equals(sub))
return 1 + strCount(str.substring(sub.length()), sub);
return strCount(str.substring(1), sub);
}
strCopies:
public boolean strCopies(String str, String sub, int n) {
if (str.length() < sub.length()) return (n <= 0);
if (str.substring(0, sub.length()).equals(sub))
return strCopies(str.substring(1), sub, n - 1);
return strCopies(str.substring(1), sub, n);
}
strDist:
public int strDist(String str, String sub) {
if (str.indexOf(sub) == -1) return 0;
if (str.substring(0, sub.length()).equals(sub)
&& str.substring(str.length() - sub.length())
.equals(sub))
return str.length();
if (!str.substring(0, sub.length()).equals(sub))
return strDist(str.substring(1), sub);
// case: (!str.substring(str.length()-sub.length()).equals(sub))
return strDist(str.substring(0, str.length() - 1), sub);
}
For further help with Coding Bat (Java), please check out my books. I am also available for tutoring.
I believe strCopies fails when more than n copies are found, where as the challenge called for true when at least n copies were found.
Simple fix:
Or alternatively, the Coding Bat solution, which short circuits recursion when the target is reached:
Good catch, Dave! I fixed that mistake in my code. The solution on Coding Bat, which I hadn’t looked at previously, is more elegant, and also more efficient.
Another tested solution for countHi2, a bit less lengthy. 🙂
public int countHi2(String str) {
if (str.length() <= 1) return 0;
if (str.substring(0, 2).equals("hi")) return 1 + countHi2(str.substring(2));
if (str.charAt(0) == 'x' && str.charAt(1) != 'x') return countHi2(str.substring(2));
return countHi2(str.substring(1));
}
Bit shorter
public int countAbc(String str) {
if(str.length()<3) return 0;
if(str.startsWith("abc") || str.startsWith("aba")) return 1 + countAbc(str.substring(1));
return countAbc(str.substring(1));
}
Shorter
public int countHi2(String str) {
if(str.length()<2) return 0;
if(str.startsWith("xhi")) return countHi2(str.substring(3));
if(str.startsWith("hi")) return 1 + countHi2(str.substring(2));
return countHi2(str.substring(1));
}
My Solution for strCount problem.
public int strCount(String str, String sub) {
if(str.length()==0 || sub.length()==0) return 0;
if(str.contains(sub)){
return 1+strCount(str.substring(str.indexOf(sub)+sub.length()),sub);
}
return 0;
}
My Solution to strCopies problem.
public boolean strCopies(String str, String sub, int n)
{
if((str.length()==0 || sub.length()==0) && n>0) return false;
if(n0){
return strCopies(str.substring(str.indexOf(sub)+1),sub,–n);
}
return false;
}