欧拉计划——31

In England the currency is made up of pound, £, and pence, p, and there are eight coins in general circulation:

1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p).

It is possible to make £2 in the following way:

1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p

How many different ways can £2 be made using any number of coins?

在英国，货币是由英镑£，便士p构成的。一共有八种钱币在流通：
1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) 和 £2 (200p).
要构造£2可以用如下方法：
1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p
允许使用任意数目的钱币，一共有多少种构造£2的方法？

package com.fk.euler;/** * Created by fengkai on 1/14/17. */public class Euler31 {public static void main(String[] args) {    int[] coin = {200,100, 50, 20, 10, 5, 2, 1};    int target = 200;    System.out.println(getCoint(coin, target, coin[0]));}private static int getCoint(int[] coin, int target, int c) {    if (c == 1) {        return 1;    }    if (target == 0) {        return 1;    }    int max = target / c;    int sum = 0;    for (int i = 0; i <= max; i++) {        int nextc = 1;        for (int j = 0; j < coin.length; j++) {            if (c == coin[j] && c != 1) {                nextc = coin[j + 1];                break;            }        }        sum += getCoint(coin, target - i * c, nextc);    }    return sum;}

}

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思路有多种，具体吧官网文档放上吧，我写的是第一个种。