Justified Text

• Time : O(A)
• Space : O(1)

vector<string> Solution::fullJustify(vector<string> &A, int B) {
    int l = 0, n = A.size();
    vector<string> res;
    while(l < n) {
        int now = A[l].length();
        int space = 0;
        int r = l + 1;
        while(r < n and now + space + 1 + A[r].length() <= B) {
            now += A[r++].length();
            space += 1;
        }
        space = B - now;
        int eqspace = r-l-1 ? space / (r-l-1) : 0;
        int gap = B - now - eqspace * (r-l-1);
        string s = "";
        if(r != n) {
            while(l < r) {
                s += A[l++] + string(eqspace, ' ');
                if(gap) {
                    s.push_back(' ');
                    gap--;
                }
            }
        } else while(l < r) s += A[l++] + " ";        
        while(s.length() < B) s.push_back(' ');
        while(s.length() > B) s.pop_back();
        res.push_back(s);
    }
    return res;
}