什么是中序表達(dá)式
前序(前綴)表達(dá)式要求每一個(gè)操作符出現(xiàn)在其操作數(shù)之前.一般不用. 寫表達(dá)式的后序表達(dá)式一般是為了便利于計(jì)算機(jī)編程中棧的實(shí)現(xiàn),所以用的較多.
具體代碼如下所示：
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package 表達(dá)式求值;import java.util.stack;/* * 中序表達(dá)式求值實(shí)現(xiàn) */public class centerexpression { public double evaluate(string expression){ //傳入中序表達(dá)式 char [] ex = expression.tochararray(); stack<double> num = new stack<>(); stack<character> ops = new stack<>(); for(int i = 0; i < ex.length; i++){ //循環(huán)將表達(dá)式依次入棧 char c = ex[i]; if(c < '9' && c > '0'){ num.push(double.parsedouble(character.tostring(c))); } else if(c == '('){ ops.push('('); } else if(c == ')'){ while(true){ char op = ops.pop(); if(op == '('){ break; } else{ switch(op){ case '+':num.push(num.pop()+num.pop());break; case '-':num.push(num.pop()-num.pop());break; case '*':num.push(num.pop()*num.pop());break; case '/':num.push(num.pop()/num.pop());break; default:break; } } } } else if(ops.empty() && (c == '+' || c == '-' || c == '*' || c == '/')){ ops.push(c); } else if(!ops.isempty() && (c == '+' || c == '-' || c == '*' || c == '/')){ char op =ops.peek(); while((op == '*' || op == '/') && (c == '+' || c == '-')){ op = ops.pop(); switch(op){ case '+':num.push(num.pop()+num.pop());break; case '-':num.push(num.pop()-num.pop());break; case '*':num.push(num.pop()*num.pop());break; case '/':num.push(num.pop()/num.pop());break; default:break; } if(ops.isempty()){ break; } else{ op = ops.peek(); } } ops.push(c); } } while(!ops.isempty()){ //處理剩余可以按計(jì)算機(jī)掃描順序處理的表達(dá)式 char op =ops.pop(); switch(op){ case '+':num.push(num.pop()+num.pop());break; case '-':num.push(num.pop()-num.pop());break; case '*':num.push(num.pop()*num.pop());break; case '/':num.push(num.pop()/num.pop());break; default:break; } } return num.pop(); } public static void main(string [] args){ centerexpression exp = new centerexpression(); system.out.println(exp.evaluate("1*2+5*3")); }} |
總結(jié)
以上所述是小編給大家介紹的java實(shí)現(xiàn)中序表達(dá)式的實(shí)例代碼，希望對(duì)大家有所幫助，如果大家有任何疑問請(qǐng)給我留言，小編會(huì)及時(shí)回復(fù)大家的。在此也非常感謝大家對(duì)服務(wù)器之家網(wǎng)站的支持！
原文鏈接：https://www.cnblogs.com/libin-blogs/archive/2018/08/08/9441231.html
