贪心算法解决0-1背包有关问题，hdu1009 为甚WA？

import java.util.Scanner;import java.util.Arrays;import java.text.DecimalFormat;class Obj implements Comparable{    int javabean;    int cat;    double scale;  public int compareTo(Object o)    {        if(scale>((Obj)o).scale)            return -1;        else if(scale<((Obj)o).scale)          return 1;        else           return 0;    }    public  boolean equals(Object o)    {        boolean f = false;        if(o instanceof Obj)        {            if(scale==((Obj)o).scale)             f = true;        }        return f;    }    public String toString()    {        String s;        s = "scale is"+scale;        return s;    }}class tanxin{public static void main(String args[]){    Obj obj[] = new Obj[1001];    for(int i=0;i<1001;i++)    {        obj[i] = new Obj();    }    Scanner keyIn = new Scanner(System.in);    int javabean;    int cat;    int M,N;    while(keyIn.hasNextInt())    {        M= keyIn.nextInt();        N= keyIn.nextInt();        if(M==-1&&N==-1)           break;        for(int i=0;i<N;i++)        {        obj[i].javabean= keyIn.nextInt();        obj[i].cat = keyIn.nextInt();      obj[i].scale = (obj[i].javabean*1.0)/obj[i].cat;        }        Arrays.sort(obj);        /*System.out.println(obj[0]);        System.out.println(obj[1]);        System.out.println(obj[2]);*/        double sum = 0;        double catsum = 0;        for(int i =0;i<N;i++)        {            if(obj[i].cat<=M-catsum)              {                  sum+=obj[i].javabean;                  catsum+=obj[i].cat;                  //System.out.println(obj[i].javabean);              }          else          {              if(obj[i].cat!=0)              {              double s= ((M-catsum)*1.0)/obj[i].cat;          //    catsum+=obj[i].cat;              sum=sum+s*obj[i].javabean;              break;            }            else            {                sum=sum +obj[i].javabean;                continue;            }              //System.out.println(obj[i].javabean*s);                        }              }        /*NumberFormat nf = NumberFormat.getNumberInstance();    nf.setMinimumFractionDigits(3);    nf.setMinimumFractionDigits(3);    String str = nf.format(sum);    System.out.println(str);*/        DecimalFormat df = new DecimalFormat();    String style="######0.000";    df.applyPattern(style);    String str = df.format(sum);    System.out.println(str);    }}    }

package com.cn.dynamic;public class Bag {    public static void main(String[] args) {        int[] w = new int[]{1, 2, 5, 6, 7};        int[] v = new int[]{1, 6, 18, 22, 28};        int r = 11;        knapsack(w,v, r);    }    private static void knapsack(int[] w, int[] v, int r) {        int[][] s = new int[w.length + 1][r + 1];        for (int i = 0; i < r + 1; i++) {            s[0][i] = 0;        }        for (int i = 1; i < w.length + 1; i++) {            s[i][0] = 0;        }        //c[i, j] = max(c[i –1, j], c[i –1, j – wi] + vi)        for (int j = 1; j <= w.length; j++) {            for (int i = 1; i <= r; i++) {                 if (w[j - 1] <= i) {                     System.out.println(i + "|" + j);                     if (s[j - 1][i] > s[j - 1][i - w[j - 1]] + v[j - 1]) {                         s[j][i] = s[j - 1][i];                     } else {                         s[j][i] = s[j - 1][i - w[j - 1]] + v[j - 1];                     }                             } else {//确定放不下了，那最大值就是s[j - 1][i]                     s[j][i] = s[j - 1][i];                 }                     }                     }        int j = 0;         for (int i = 0; i < s.length;) {                          try {                 System.out.print(s[i][j] + "  ");                 j++;             }catch(ArrayIndexOutOfBoundsException e) {                 i++;                 j=0;                 System.out.println();             }         }    }}