Leetcode 68. 文本左右对齐

class Solution {
public:
    vector<string> fullJustify(vector<string>& words, int m) {
        vector<string> res;
        int n = words.size();
        vector<int> cnt(n);
        for (int i = 0; i < n; i ++ )
            cnt[i] += words[i].size();
        
        int s = 0, num = 0, l = 0, N = 0; // r 行数 s 每行单词格子
        for (int i = 0; i < n; i ++ ) {
            s = 0, num = 0, l = i, N = 0;
            while (i < n && N + cnt[i] + (i != l) <= m) 
                s += cnt[i], num ++ , N += cnt[i] + (i != l), i ++ ;
            i -- ;
            // 格子数量
            int k = 0, mod = 0;
            if (num != 1) {
                k = (m - s) / (num - 1);
                mod = (m - s) % (num - 1);
            }
            // int k = 0, mod = 0;
            string ans;
            if (i != n - 1) {
            for (int j = l; j < i; j ++ )
            {
                ans += words[j];
                int a = k;
                while (a -- ) ans += ' ';
                if (mod -- > 0) ans += ' '; 
            }
            ans += words[i];
            }
            else if (i == n - 1) {
                for (int j = l; j <= i; j ++ ) {
                    ans += words[j];
                    if (num - 1 > 0) ans += ' ', num -- ;
                }
            }
            while (ans.size() < m) ans += ' ';
            res.push_back(ans);
        }
        return res;
    }
};