How to Remove Vowels from a String in C++?

Given a string S, remove the vowels ‘a’, ‘e’, ‘i’, ‘o’, and ‘u’ from it, and return the new string.

Example 1:
Input: “leetcodeisacommunityforcoders”
Output: “ltcdscmmntyfrcdrs”

Example 2:
Input: “aeiou”
Output: “”

S consists of lowercase English letters only.
1 <= S.length <= 1000

Loop and Remove

The usual approach will be looping the string and check each character. Ignore the vowels or otherwise push it to the result string.

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class Solution {
public:
    string removeVowels(string S) {
        string s = "";
        for (const auto &n: S) {
            if (string("aeiou").find(n) == string::npos) {
                s.push_back(n);  // s += n;
            }
        }
        return s;
    }
};

class Solution {
public:
    string removeVowels(string S) {
        string s = "";
        for (const auto &n: S) {
            if (string("aeiou").find(n) == string::npos) {
                s.push_back(n);  // s += n;
            }
        }
        return s;
    }
};

Using Modern C++ std::accumulate()

With the std::accumulate() in Modern C++ e.g. C++14, we need to pass the begin and end iterators, the initial value which is set to a mutable string/vector, and a accmulator function.

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class Solution {
public:
    string removeVowels(string S) {
        return std::accumulate(begin(S), end(S), std::string{}, [](auto &a, auto &b) {
            if (string("aeiou").find(b) == string::npos) {
                return a + b; 
            } 
            return a; // b is vowel, ignore
        });
    }
};

class Solution {
public:
    string removeVowels(string S) {
        return std::accumulate(begin(S), end(S), std::string{}, [](auto &a, auto &b) {
            if (string("aeiou").find(b) == string::npos) {
                return a + b; 
            } 
            return a; // b is vowel, ignore
        });
    }
};

It is worth pointing out that the “” in C++ is interpreted to char* by default, that is why we need to explicitly cast it to string type before using the find() method.

See also: Teaching Kids Programming – Remove Vowels from a String

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