Ein Quell der Freude

#include <algorithm>

std::vector<int> spaces = std::accumulate(lines.begin() + 1, lines.end(),
        std::vector<int>(max_length, 1), [](auto acc, auto line) {
    std::vector<int> tmp(acc.size(), 0);
    std::transform(line.begin(), line.end(), acc.begin(), tmp.begin(), 
            [](wchar_t ch, int b) {
        return b && (ch == L' '); 
    });
    return tmp;
});