//扔 n 个骰子,向上面的数字之和为 S。给定 Given n,请列出所有可能的 S 值及其相应的概率
public class Solution {
/**
* @param n an integer
* @return a list of Map.Entry<sum, probability>
*/
public List<Map.Entry<Integer, Double>> dicesSum(int n) {
// Write your code here
// Ps. new AbstractMap.SimpleEntry<Integer, Double>(sum, pro)
// to create the pair.
List<Map.Entry<Integer, Double>> results =
new ArrayList<Map.Entry<Integer, Double>>();
double[][] f = new double[n + 1][6 * n + 1];
for (int i = 1; i <= 6; ++i)
f[1][i] = 1.0 / 6;
for (int i = 2; i <= n; ++i)
for (int j = i; j <= 6 * n; ++j) {
for (int k = 1; k <= 6; ++k)
if (j > k)
f[i][j] += f[i - 1][j - k];
f[i][j] /= 6.0;
}
for (int i = n; i <= 6 * n; ++i)
results.add(new AbstractMap.SimpleEntry<Integer, Double>(i, f[n][i]));
return results;
}
}