103 lines
2.6 KiB
Java
103 lines
2.6 KiB
Java
package chelper;
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import io.InputReader;
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import io.OutputWriter;
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import misc.GCJSolution;
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import misc.SimpleSavingChelperSolution;
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public class TaskD extends GCJSolution {
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public void solve(int testNumber, InputReader in, OutputWriter out) {
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wrapSolve(testNumber, in, out);
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}
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double[][][] dp;
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public TaskD() {
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super();
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dp = new double[101][101][101];
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for (int c = 0; c <= 100; c++) {
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for (int b = 0; b <= 100; b++) {
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for (int a = 0; a <= 100; a++) {
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dp[a][b][c] = Double.NaN;
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}
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}
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}
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dp[0][0][0] = 0;
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get(0, 0, 100);
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// for (int c = 0; c <= 2; c++) {
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// for (int b = 0; b <= 2; b++) {
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// for (int a = 0; a <= 2; a++) {
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// System.out.println(a + " " + b + " " + c + " " + dp[a][b][c]);
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// }
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// }
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// }
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}
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@Override
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public void solve(int testNumber) {
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int n = in.nextInt();
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out.println(get(0, 0, n));
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}
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double get(int a, int b, int c) {
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if (a < 0 || b < 0 || c < 0) {
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return 0;
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}
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if (Double.isNaN(dp[a][b][c])) {
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calc(a, b, c);
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}
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return dp[a][b][c];
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}
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void calc(int a, int b, int c) {
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double aa = a;
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double bb = 2 * b;
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double cc = 3 * c;
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double n = aa + bb + cc;
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//////////////
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dp[a][b][c] = 0;
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if (n >= 3) {
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dp[a][b][c] += (cc / n) * (2 / (n - 1)) * (1 / (n - 2)) * (get(a + 0, b + 0, c - 1) + 1 + 0);
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dp[a][b][c] += (cc / n) * (2 / (n - 1)) * (aa / (n - 2)) * (get(a + 0, b + 0, c - 1) + 1 + 1);
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dp[a][b][c] += (cc / n) * (2 / (n - 1)) * (bb / (n - 2)) * (get(a + 2, b - 1, c - 1) + 1 + 0);
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dp[a][b][c] += (cc / n) * (2 / (n - 1)) * ((cc - 3) / (n - 2)) * (get(a + 1, b + 1, c - 2) + 1 + 0);
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}
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if (n >= 2) {
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dp[a][b][c] += (cc / n) * (aa / (n - 1)) * (get(a - 1, b + 1, c - 1) + 1 + 1);
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dp[a][b][c] += (cc / n) * (bb / (n - 1)) * (get(a + 1, b + 0, c - 1) + 1 + 0);
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dp[a][b][c] += (cc / n) * ((cc - 3) / (n - 1)) * (get(a + 0, b + 2, c - 2) + 1 + 0);
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}
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//////////////
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if (n >= 2) {
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dp[a][b][c] += (bb / n) * (1 / (n - 1)) * (get(a + 0, b - 1, c + 0) + 1 + 0);
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dp[a][b][c] += (bb / n) * (aa / (n - 1)) * (get(a + 0, b - 1, c + 0) + 1 + 1);
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dp[a][b][c] += (bb / n) * ((bb - 2) / (n - 1)) * (get(a + 2, b - 2, c + 0) + 1 + 0);
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dp[a][b][c] += (bb / n) * (cc / (n - 1)) * (get(a + 1, b + 0, c - 1) + 1 + 0);
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}
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//////////////
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dp[a][b][c] += (aa / n) * (get(a - 1, b + 0, c + 0) + 1);
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}
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}
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