n 个骰子的点数

把 n 个骰子仍在地上，求点数和为 s 的概率。

java：

 public List<Map.Entry<Integer, Double>> dicesSum(int n) {
     final int face = 6;
     final int pointNum = face * n;
     long[][] dp = new long[n + 1][pointNum + 1];

     for (int i = 1; i <= face; i++)
         dp[1][i] = 1;

     for (int i = 2; i <= n; i++)
         for (int j = i; j <= pointNum; j++)     /* 使用 i 个骰子最小点数为 i */
             for (int k = 1; k <= face && k <= j; k++)
                 dp[i][j] += dp[i - 1][j - k];

     final double totalNum = Math.pow(6, n);
     List<Map.Entry<Integer, Double>> ret = new ArrayList<>();
     for (int i = n; i <= pointNum; i++)
         ret.add(new AbstractMap.SimpleEntry<>(i, dp[n][i] / totalNum));

     return ret;
 }