“Write a program that outputs all possibilities to put + or - or nothing between the numbers 1, 2, …-优快云博客

本文链接：https://blog.youkuaiyun.com/juan3juan/article/details/88387100

本文介绍了一个使用Java编写的程序，该程序能够找出所有可能的方式，在数字1到9之间插入加号、减号或什么都不插入，使得最终的数学表达式结果等于100。通过将问题转换为三进制数的遍历，程序巧妙地解决了这个数学谜题。

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Question--

“Write a program that outputs all possibilities to put + or - or nothing between the numbers 1, 2, …, 9 (in this order) such that the result is always 100”

Java

public static void main(String[] args) throws IOException, ScriptException {

String[] o = { "", "-", "+" };

ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine engine = manager.getEngineByName("js");

       int sum = 0;
       for (int i = 5; i <= combinations; i++) {
           int tmp = Integer.parseInt(Integer.toString(i, 3), 10); //translate to base 3

String str = String.format("%08d", tmp);

           int[] p = new int[8];
           for (int j = 0; j < 8; j++) {
               p[j] = str.charAt(j) - 48;
           }

String resultS = "1" + o[p[0]] + "2" + o[p[1]] + "3" + o[p[2]] + "4" + o[p[3]] + "5" + o[p[4]] + "6"
+ o[p[5]] + "7" + o[p[6]] + "8" + o[p[7]] + "9";

           int result = (Integer) engine.eval(resultS);
           if (result == 100) {
               sum++;
               solutions.add(resultS);
           }
       }
       for (int i = 0; i < solutions.size(); i++) {
           System.out.print(solutions.get(i) + "\n");
       }
       System.out.print(sum);
   }