四则运算(C#版)
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/// <summary>
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/// 四则运算
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/// </summary>
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/// <returns>返回结果</returns>
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public int EvaluateExpression()
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{
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SeqStack<char> optr = new SeqStack<char>(20); //存放操作符栈
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SeqStack<int> opnd = new SeqStack<int>(20); //存放操作数栈
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optr.Push('#');
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char c = (char)Console.Read(); //读取每一个数
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bool isLoop = true; //定义一个循环变量
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char tmp = default(char); //临时操作符
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int a = 0; //计算数1
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int b = 0; //计算数2
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while (isLoop)
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{
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if (c == '#' && opnd.Top == 0)
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isLoop = false;
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if (c != '+' && c != '-' && c != '*' && c != '/' && c != '(' && c != ')' && c != '#')//不是操作数入数据栈
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{
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opnd.Push(((int)c)- 48);
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c = (char)Console.Read();
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}
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else
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{
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switch (Precede(optr.GetTop(), c))
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{
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case '<':
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optr.Push(c);
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c = (char)Console.Read();
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break;
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case '=':
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optr.Pop();
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c = (char)Console.Read();
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break;
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case '>':
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tmp = optr.Pop();
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a = opnd.Pop();
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b = opnd.Pop();
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opnd.Push(Operate(b, tmp, a));
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break;
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default:
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throw new System.ExecutionEngineException("输入错误格式错误!");
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break;
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}
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}
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}
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return opnd.Pop();
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}
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//判断优先级
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private char Precede(char optr1, char optr2)
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{
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//定义一个比较结果(用二维数组存下来)
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char[,] optrTable = {
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{ '>', '>', '<', '<', '<', '>', '>' },
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{ '>', '>', '<', '<', '<', '>', '>' },
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{ '>', '>', '>', '>', '<', '>', '>' },
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{ '>', '>', '>', '>', '<', '>', '>' },
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{ '<', '<', '<', '<', '<', '=', '?' },
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{ '>', '>', '>', '>', '?', '>', '>' },
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{ '<', '<', '<', '<', '<', '?', '=' } };
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int x = 0, y = 0;//申明存符号转化后的整数
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//定义一个符号数组
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char[] optrs ={ '+', '-', '*', '/', '(', ')', '#' };
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for (int i = 0; i < optrs.Length; ++i)
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{
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if (optr1 == optrs[i])
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x = i;
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if (optr2 == optrs[i])
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y = i;
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}
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return optrTable[x, y];
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}
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//计算两值,得出相应结果
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private int Operate(int a, char optr, int b)
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{
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int result = default(int);
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switch (optr)
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{
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case '+':
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result = a + b;
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break;
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case '-':
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result = a - b;
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break;
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case '*':
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result = a * b;
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break;
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case '/':
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result = a / b;
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break;
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default:
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break;
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}
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return result;
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}
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以上代码仅贡参考,如有雷同,纯属巧合.
中间还可以根据自己的需求改进~~