atcoderDP/Sushi.java at master · KTong821/atcoderDP · GitHub

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importjava.util.*;
importjava.io.*;

publicclassSushi {

publicstaticvoidmain(String[] args) throwsIOException {
BufferedReaderbr = newBufferedReader(newInputStreamReader(System.in));
doublen = Double.parseDouble(br.readLine());
String[] s = br.readLine().split(" ");
int[] arr = newint[4];
for (intq = 0; q < n; q++) {
arr[Integer.parseInt(s[q])]++;
 }

intm1 = arr[1] + arr[2] + arr[3];
intm2 = arr[2] + arr[3];
intm3 = arr[3];

intt = (int) n + 1;
double [][][] dp = newdouble[t][t][t];
for (intk = 0; k <= m3; k++) {
for (intj = 0; j <= m2-k; j++) {
for (inti = 0; i <= m1-j-k; i++) {
// System.out.println(i + " " + j + " " + k);
if (i == 0 && j == 0 && k == 0)
continue;

intsum = i + j + k;
dp[i][j][k] = n / sum;

if (i != 0)
dp[i][j][k] += (double) dp[i - 1][j][k] * i / sum;
if (j != 0)
dp[i][j][k] += (double) dp[i + 1][j - 1][k] * j / sum;
if (k != 0)
dp[i][j][k] += (double) dp[i][j + 1][k - 1] * k / sum;
 }
 }
 }

System.out.println(dp[arr[1]][arr[2]][arr[3]]);

	}

}