四则运算二
一、程序设计思路
在详细的查看了观察《冀教版数学二年级上册口算练习》文档之后，可以发现：1.算式中每个数不能超过100，运算结果不能超过100。2.运算结果必须得是正整数，除法不能出现余数。3.乘法算式的范围在9 X 9乘法表内，除法算式同样。4.可以出现一部分混合运算，但仅限于加减法而且不带括号优先级。
根据上述规则，可以采用如下方式产生算式：
首先可以明确，在一定范围内，随机数的产生结果不会有大规模的重复现象，查重很耗费时间。
操作符通过1-4的随机数产生，一个数对应一个操作符。
对于加法算式，第一个操作数opre1直接在1-99内生成，第二个操作数在100-opre1到1之间生成。
对于减法算式，第一个操作数opre1直接在1-99内生成，第二个操作数在opre1到1之间生成。
对于乘法，两个操作数均在1-9内产生。
对于除法，先产生两个1-9之间的随机数opre1、opre2，然后让opre1 = opre1*opre2，opre2不变，opre1作为算式的答案。
对于三个操作数的混合运算，原理同上。
二、源代码
1 import java.util.ArrayList; 2 import java.util.List; 3 import java.util.Random; 4 import java.util.Scanner; 5 import java.util.Set; 6 import java.util.Vector; 7 8 public class GradeTwo { 9 private static String opera = "+-*/"; 10 public static Vector<String> pro = new Vector<String>(); 11 public static Vector<String> key = new Vector<String>(); 12 //public static Vector<String> key1 = new Vector<String>(); 13 public static String[]result1; 14 public static int[]end = new int[3]; 15 public static void solve(String[]list) { 16 result1 = new String[list.length]; 17 for(int i = 0;i<list.length;++i) 18 result1[i]= list[i]; 19 } 20 public static void clear() { 21 pro.clear(); 22 key.clear(); 23 } 24 public static int isInteger(int c1, int c2, char opera) { 25 int result = 0; 26 int result1 = 0; 27 switch (opera) { 28 case '+': 29 result = c1 + c2; 30 break; 31 case '-': 32 result = c1 - c2; 33 break; 34 case '*': 35 result = c1 * c2; 36 break; 37 case '/': 38 result = c1 / c2; 39 result1 = c1 % c2; 40 break; 41 } 42 if (result >= 0 && result <= 100 && result1 == 0) 43 return result; 44 else 45 return -1; 46 } 47 48 public static String getPoly() { 49 String poly = ""; 50 // Random random = new Random(); 51 // 52 // int c1; 53 // int c2; 54 // int result; 55 // char operac; 56 // boolean flag = true; 57 // do { 58 // c1 = random.nextInt(100) + 1; 59 // c2 = random.nextInt(100) + 1; 60 // operac = opera.charAt(random.nextInt(4)); 61 // if (operac == '*') 62 // poly = c1 + " × " + c2 + " = "; 63 // if (operac == '/') 64 // poly = c1 + " ÷ " + c2 + " = "; 65 // if (operac == '+') 66 // poly = c1 + " + " + c2 + " = "; 67 // if (operac == '-') 68 // poly = c1 + " - " + c2 + " = "; 69 // /*for (int i = 0;i<pro.size();++i) { 70 // if (poly.equals(pro.get(i))) { 71 // flag = false; 72 // break; 73 // } 74 // }*/ 75 // } while (!flag || (result = isInteger(c1, c2, operac)) < 0); 76 // pro.add(poly); 77 // key.add(String.valueOf(result)); 78 Random random = new Random(); 79 //产生0.9的两位运算,0.1的三位运算 80 char operate; 81 char operate1; 82 int operand1 = 0; 83 int operand2 = 0; 84 int operand3 = 0; 85 int result; 86 int percent = random.nextInt(100)+1; 87 if(percent<=90) { 88 operate = opera.charAt(random.nextInt(4)); 89 switch(operate) { 90 case '+': 91 operand1 = random.nextInt(100); 92 operand2 = random.nextInt(100-operand1); 93 poly = operand1+" + "+operand2+" = "; 94 break; 95 case '-': 96 operand1 = random.nextInt(100)+1; 97 operand2 = random.nextInt(operand1); 98 poly = operand1+" - "+operand2+ " = "; 99 break; 100 case '*': 101 operand1 = random.nextInt(9)+1; 102 operand2 = random.nextInt(9)+1; 103 poly = operand1+" × "+operand2+ " = "; 104 break; 105 case '/': 106 operand1 = random.nextInt(9)+1; 107 operand2 = random.nextInt(9)+1; 108 operand1 = operand1*operand2; 109 poly = operand1+" ÷ "+operand2+ " = "; 110 break; 111 } 112 result = isInteger(operand1, operand2, operate); 113 key.add(String.valueOf(result)); 114 }else { 115 operate = opera.charAt(random.nextInt(2)); 116 operate1 = opera.charAt(random.nextInt(2)); 117 if(operate=='+') { 118 operand1 = random.nextInt(100); 119 operand2 = random.nextInt(100-operand1); 120 if(operate1=='+') { 121 operand3 = random.nextInt(100-operand1-operand2); 122 poly = operand1+" + "+operand2+" + "+operand3+" = "; 123 }else { 124 operand3 = random.nextInt(operand1+operand2); 125 poly = operand1+" + "+operand2+" - "+operand3+" = "; 126 } 127 }else { 128 operand1 = random.nextInt(100)+1; 129 operand2 = random.nextInt(operand1); 130 if(operate1=='+') { 131 operand3 = random.nextInt(100-operand1+operand2); 132 poly = operand1+" - "+operand2+" + "+operand3+" = "; 133 }else { 134 operand3 = random.nextInt(operand1-operand2); 135 poly = operand1+" - "+operand2+" - "+operand3+" = "; 136 } 137 } 138 result = isInteger(operand1, operand2, operate); 139 result = isInteger(result, operand3, operate1); 140 key.add(String.valueOf(result)); 141 } 142 pro.add(poly); 143 return poly; 144 } 145 public static void End(String[]list){ 146 //int[]result = new int[3]; 147 end[0] = 0; 148 end[1] = 0; 149 end[2] = 0; 150 int len = list.length; 151 for(int i = 0;i<len;++i) { 152 if(key.get(i).equals(list[i]))end[0]++; 153 else { 154 if(list[i].equals(""))end[2]++; 155 else end[1]++; 156 } 157 } 158 return; 159 } 160 public static void main(String[]args) { 161 // int result = isInteger(55,13,'-'); 162 // result = isInteger(result,19,'-'); 163 // System.out.println(result); 164 Scanner s = new Scanner(System.in); 165 System.out.print("输入题目数量:"); 166 int num = s.nextInt(); 167 String str = null; 168 for(int i = 1;i<=num;++i) { 169 str = GradeTwo.getPoly(); 170 System.out.println(str); 171 } 172 } 173 }
三、验证截图
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