Solution.java

class Solution {
    public String[] splitMessage(String message, int limit) {
        int n = message.length();
        int sa = 0;
        String[] ans = new String[0];
        for (int k = 1; k <= n; ++k) {
            int lk = (k + "").length();
            sa += lk;
            int sb = lk * k;
            int sc = 3 * k;
            if (limit * k - (sa + sb + sc) >= n) {
                int i = 0;
                ans = new String[k];
                for (int j = 1; j <= k; ++j) {
                    String tail = String.format("<%d/%d>", j, k);
                    String t = message.substring(i, Math.min(n, i + limit - tail.length())) + tail;
                    ans[j - 1] = t;
                    i += limit - tail.length();
                }
                break;
            }
        }
        return ans;
    }
}