Text Justification greedy

思路：

贪心。时间复杂度O(N)，空间复杂度O(1)。

class Solution {private:/**    add space to a target line    @param s : target line    @param i : current space's number    @param n : interspace sum    @param L : space sum    @param is_last : whether is the last line    @return*/void addSpaces(string &s, int i, int n, int L, bool is_last) {    if(n < 1 || i > n - 1) return;    int spaces = is_last ? 1 : (L/n + (i < (L%n) ? 1 : 0));    s.append(spaces, ' ');}/**    connect words[begin, end] to a line    @param words    @param begin    @param end    @param len : the length of words[begin, end]    @param maxWidth    @param is_last : whether if is the last line    @return the connected line*/string connect(vector<string> &words, int begin, int end, int len, int maxWidth, bool is_last) {    string s;    int n = end - begin + 1;// words number    for(int i = 0; i < n; ++i) {        s += words[begin + i];        addSpaces(s, i, n - 1, maxWidth - len, is_last);    }    if(s.size() < maxWidth) {        s.append(maxWidth - s.size(), ' ');    }    return s;}public:    vector<string> fullJustify(vector<string>& words, int maxWidth) {        vector<string> res;        const int n = words.size();        int begin = 0, len = 0;//current line's starting point, current line's length        for(int i = 0; i < n; ++i) {            if(len + words[i].size() + (i - begin) > maxWidth) {                res.push_back(connect(words, begin, i-1, len, maxWidth, false));                begin = i;                len = 0;            }            len += words[i].size();        }        res.push_back(connect(words, begin, n-1, len, maxWidth, true));        return res;    }};