C++: How do I split a string into evenly-sized smaller strings?

My solution: std::vector<std::string> split(std::string const & s, size_t count) { size_t minsize = s.size()/count; int extra = s.size() - minsize * count; std::vector<std::string> tokens; for(size_t i = 0, offset=0 ; i < count ; ++i, --extra) { size_t size = minsize + (extra>0?1:0); if ( (offset + size) < s.size()) tokens.push_back(s.substr(offset,size)); else tokens.push_back(s.substr(offset, s.size() - offset)); offset += size; } return tokens; } Test code: int main() { std::string s; while (std::cin >> s) { std::vector<std::string> tokens = split(s, 5); //output std::copy(tokens.begin(), tokens.end(), std::ostream_iterator<std::string>(std::cout, ", ")); std::cout << std::endl; } } Input: 012345 0123456 01234567 012345678 0123456789 01234567890 Output: 01, 2, 3, 4, 5, 01, 23, 4, 5, 6, 01, 23, 45, 6, 7, 01, 23, 45, 67, 8, 01, 23, 45, 67, 89, 012, 34, 56, 78, 90, Online Demo : http://ideone.com/gINtK This solution tends to make the tokens even, i.e all tokens may not be of same size.

It's enough to know the length of substrings; Assume m is size() of your string: int k = (m%n == 0)? n : n-m%n; Then k of substrings should be of length m/n and n-k of length m/n+1.

Try http://www.cplusplus.com/reference/string/string/substr/.

You get iterators for where you want to split it, then use those to construct new strings. For example: std::string s1 = "string to split"; std::string::iterator halfway = s1.begin() + s1.size() / 2; std::string s2(s1.begin(), halfway); std::string s3(halfway, s1.end());

Lets's say the string length is L and it must be split in n substrings. # Find the next multiple of `n` greater than or equal to `L` L = 9 n = 5 LL = n * (L / n) if LL < L: LL += n # Split a string of length LL into n equal sizes. The string is at # most (n-1) longer than L. lengths = [(LL / n) for x in range (n)] # Remove one from the first (or any) (LL-L) elements. for i in range (LL-L): lengths [i] = lengths [i] - 1 # Get indices from lengths. s = 0 idx = [] for i in lengths: idx.append (s) s = s + i idx.append (L) print idx EDIT: OK, OK, I forgot it should be C++. EDIT: Here it goes ... #include <vector> #include <iostream> unsigned int L = 13; unsigned int n = 5; int main () { int i; unsigned int LL; std::vector<int> lengths, idx; /* Find the next multiple of `n` greater than or equal to `L` */ LL = n * (L / n); if (LL < L) LL += n; /* Split a string of length LL into n equal sizes. The string is at most (n-1) longer than L. */ for (i = 0; i < n; ++i) lengths.push_back (LL/n); /* Remove one from the first (or any) (LL-L) elements. */ for (i = 0; i < LL - L; ++i) --lengths [i]; /* Get indices from lengths. */ int s = 0; for (auto &ii: lengths) { idx.push_back (s); s += ii; } idx.push_back (L); for (auto &i : idx) std::cout << i << " "; std::cout << std::endl; return 0; }