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  1. final class opAlgo
  2. {
  3.   //    private static final int[] values = {3, 7, 8, 10, 50, 100};
  4.   private static final int[] values = {1, 2, 3};
  5.   private static final char[] ops = {'+', '-', '/', '*'};
  6.  
  7.   public static void main (String[] args)
  8.   {
  9.       try(java.io.BufferedReader br = new java.io.BufferedReader(
  10.               new java.io.InputStreamReader(System.in))) {
  11.  
  12.           opAlgo solver = new opAlgo();
  13.  
  14.           while (true) {
  15.               System.out.print("Enter a target value: ");
  16.               int target = Integer.parseInt(br.readLine());
  17.               System.out.println(solver.solve(target));
  18.               break;
  19.           }
  20.       }
  21.       catch (java.io.IOException | java.lang.IllegalArgumentException e) {
  22.  
  23.       }
  24.  
  25.   }
  26.  
  27.   private String solve(final int target) {
  28.       java.lang.StringBuilder ans = new java.lang.StringBuilder();
  29.       java.util.LinkedHashSet<Integer> set = new java.util.LinkedHashSet<Integer>();
  30.       java.util.List<Character> operands= new java.util.Vector<Character>();
  31.  
  32.       for (int n : opAlgo.values) {
  33.           set.add(n);
  34.           if (n == target) {
  35.               ans.append('\n' + Integer.toString(n));
  36.           }
  37.           looper(n, target, ans, set, operands);
  38.           set.remove(n);
  39.       }
  40.       ans.append("\n-------------------------\n");
  41.       return ans.toString();
  42.   }
  43.  
  44.   private void looper(int total, int target, java.lang.StringBuilder ans, 
  45.           java.util.LinkedHashSet<Integer> set, java.util.List<Character> operands) {
  46.  
  47.       for (int n : opAlgo.values) {
  48.           if (set.add(n)) {
  49.               for (char op : opAlgo.ops) {
  50.                   operands.add(op);
  51.                   int cul = chrToValue(total, op, n);
  52.                   if (cul == target) {
  53.                       String exp = opAlgoFormat(set, operands);
  54.                       ans.append('\n' + exp);
  55.                   }
  56.                   looper(cul, target, ans, set, operands);
  57.                   operands.remove(operands.size() - 1);
  58.               }
  59.               set.remove(n);
  60.           }
  61.       }
  62.   }
  63.  
  64.   private String opAlgoFormat(java.util.LinkedHashSet<Integer> set, 
  65.           java.util.List<Character> values) {
  66.  
  67.       java.util.Iterator<Integer> iter = set.iterator();
  68.       String toString = new String(Integer.toString(iter.next()));
  69.       int t = 0;
  70.       char prev = ' ';
  71.       while (iter.hasNext()) {
  72.           int v = iter.next();
  73.           if ((values.get(t) == '/' || values.get(t) == '*') && (prev == '+' || prev == '-')) {
  74.               toString = "(" + toString + ")";
  75.           }
  76.  
  77.           toString += " " + Character.toString(values.get(t)) + " " + Integer.toString(v);
  78.           prev = values.get(t++);
  79.       }
  80.       return toString;
  81.   }
  82.  
  83.   private int chrToValue(int n1, char op, int n2) {
  84.       switch(op) {
  85.       case '+':
  86.           return n1 + n2;
  87.       case '-':
  88.           return n1 - n2;
  89.       case '/':
  90.           if (n1 % n2 == 0)
  91.               return n1 / n2;
  92.           return Integer.MAX_VALUE;
  93.       case '*':
  94.           return n1 * n2;
  95.       }
  96.       throw new java.lang.IllegalArgumentException();
  97.   }
  98. }
Success #stdin #stdout 0.07s 381248KB
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stdin
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stdout
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Enter a target value: 
1 + 2 + 3
1 * 2 * 3
1 + 3 + 2
1 * 3 * 2
2 + 1 + 3
2 / 1 * 3
2 * 1 * 3
2 + 3 + 1
2 * 3
2 * 3 / 1
2 * 3 * 1
3 + 1 + 2
3 / 1 * 2
3 * 1 * 2
3 + 2 + 1
3 * 2
3 * 2 / 1
3 * 2 * 1
-------------------------
https://ideone.com/pyTnfv
language:
Java (12.0.1)
created:
10 years ago
visibility:
public

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