http://poj.org/problem?id=1737 import java.util.*; import java.math.*; public class Main { BigInteger[] ans = new BigInteger[52]; public Main() { DP(); solve(); } //求组合数 BigInteger combinationNum(int n, int m) { BigInteger ret = new BigInteger("1"); int i; for (i = 0; i < m; ++i) { ret = ret.multiply(new BigInteger(n - i + "")); ret = ret.divide(new BigInteger(i + 1 + "")); } return ret; } void DP() { ans[1] = new BigInteger("1"); ans[2] = new BigInteger("1"); int i, j; BigInteger tmp = new BigInteger("0"); BigInteger com = new BigInteger("0"); for (i = 3; i <= 50; ++i) { ans[i] = new BigInteger("0"); for (j = 1; j < i; ++j) { com = combinationNum(i - 2, j - 1); tmp = ans[j].multiply(ans[i - j]); tmp = tmp.multiply(com); tmp = tmp.multiply(new BigInteger(((long)1 << j) - 1 + "")); ans[i] = ans[i].add(tmp); } } //for (i = 1; i <= 50; ++i) // System.out.println(i + ": " + ans[i]); } void solve() { int n; Scanner cin = new Scanner(System.in); while (true) { n = cin.nextInt(); if (n == 0) return; System.out.println(ans[n]); } } public static void main(String args[]) { new Main(); } }
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