满足条件的排列组合,该如何解决

满足条件的排列组合
假设有一个随机数列{10,20，5，......} 
求其中相加为100的所数有组合，比方{{20，20，20，20，20},{20,20,20，10，5，5，20},......}

[解决办法]
子集求和问题 我给你代码 用的是非递归的回溯法

Java code

package com.haojia.algorithm;import java.util.Random;/** * 子集求和 非递归回溯 效率高 *  * @author July *  */public class SubSum {    // 计算    public static void compute(int[] data, int sum) {        boolean[] state = new boolean[data.length];        int p = 0;        int temp = 0;        int count = 0;        while (true) {            // 累加开始            while (p != data.length) {                if (!state[p]) {                    state[p] = true;                    temp += data[p];                    if (temp == sum) {                        count++;                        print(data, sum, state);                    }                    if (temp > sum) {                        state[p] = false;                        temp -= data[p];                    }                }                p++;            }            // 累加结束            // 回溯开始            while (state[p - 1]) {                state[p - 1] = false;                temp -= data[p - 1];                p--;                if (p == 0) {                    System.out.println(count + "种方法");                    return;                }            }            while (!state[p - 1]) {                p--;                if (p == 0) {                    System.out.println(count + "种方法");                    return;                }            }            state[p - 1] = false;            temp -= data[p - 1];            // 回溯结束        }    }    // 格式化打印    public static void print(int[] data, int sum, boolean[] state) {        StringBuffer s = new StringBuffer();        for (int i = 0; i < data.length; i++) {            if (state[i]) {                s.append(data[i]);                s.append("+");            }        }        System.out.println(s.substring(0, s.length() - 1) + "=" + sum);    }    public static void main(String[] args) {        Random r = new Random();        int[] data = new int[20];        for (int i = 0; i < data.length; i++) {            data[i] = r.nextInt(100);        }        compute(data, 100);    }}
[解决办法]
Java code
package cxz.math;import java.util.Calendar;public class Cal {  int[] data = { 5, 5, 5, 5, 20, 20, 20, 20, 10, 10, 10, 5, 5, 10, 10, 20, 20, 10, 10, 5 };  int total = 100;  /////////////////  int nt = data.length;  int[] s = new int[nt];  int m[] = { 1, 0 };  int fm = 0;  int no = 0;  public static void main(String[] args) {    Calendar cstart = Calendar.getInstance();    Cal g = new Cal();    g.cal();    Calendar cend = Calendar.getInstance();    System.out.println("花费时间" + (cend.getTimeInMillis() - cstart.getTimeInMillis()) / 1000.0 + "秒");  }  public void cal() {    fm = 0;    f(0);  }  private void f(int n) {    if (n == nt) {      return;    }    for (int i = 0; i < m.length; i++) {      s[n] = m[i];      if (m[i] == 1) {        fm += data[n];        if (fm == total) {          no++;          show();        }      }      if (fm < total)        f(n + 1);      if (m[i] == 1) {        fm -= data[n];      }    }  }  void show() {    StringBuffer buf = new StringBuffer();    for (int L = 0; L < data.length; L++)      buf.append((s[L] == 1 ? (data[L] + " ") : ""));    System.out.println(no + ":" + buf.toString());  }}