求写一个方法 要求传入任意一个算式 如：“2+3*5+3/2” 求该方法算出结果 这个必须用递归怎么做？
我没有用过递归，这个题我是直接拆分成数组做出来了，但是要求我用递归，知道的说下吧！最好是代码配合原理的说下，谢谢了
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- Java code
public static int countString(String s){ int num = 0 ; String[] ss = s.split("[\\+\\-\\*/\\(\\)]") ; if( ss.length>2){ int si = 0 ; if( (si=s.indexOf("("))!=-1){ num = countString(s.substring(si+1 , s.indexOf(")"))); num =countString(s.substring(0 , si)+num + s.substring(s.indexOf(")")+1)); }else if((si=s.replaceAll("[\\*/]", ",").indexOf(","))!= -1 ){ System.out.println(si); int statr = s.substring(0, si).replaceAll("[\\+\\-\\*/\\(\\)]", ",").lastIndexOf(",") ; int end = s.substring( si+1).replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; num = countString(s.substring(statr==-1?0:statr, end==-1?s.length():end+2)); num =countString(s.substring(0 , statr==-1?0:statr)+num + s.substring(end==-1?s.length():end+2)); }else if((si=s.replaceAll("[\\+\\-]", ",").indexOf(","))!= -1 ){ int statr = s.substring(0, si).replaceAll("[\\+\\-\\*/\\(\\)]", ",").lastIndexOf(",") ; int end = s.substring( si+1).replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; num = countString(s.substring(statr==-1?0:statr, end==-1?s.length():end+2)); num = countString(s.substring(0 , statr==-1?0:statr)+num + s.substring(end==-1?s.length():end+2)); } }else{ int index =s.replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; if(index!=-1){ String s2 = s.substring(index,index+1) ; if(s2.equals("*")) num = new Integer(ss[0]) * new Integer(ss[1]) ; if(s2.equals("/")) num = new Integer(ss[0]) / new Integer(ss[1]) ; if(s2.equals("+")) num = new Integer(ss[0]) + new Integer(ss[1]) ; if(s2.equals("-")) num = new Integer(ss[0]) - new Integer(ss[1]) ; }else{ num = new Integer(s) ; } } return num; }
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- Java code
public static int countString(String s){ System.out.println(s); int num = 0 ; String[] ss = s.split("[\\+\\-\\*/\\(\\)]") ; if( ss.length>2){ int si = 0 ; if( (si=s.indexOf("("))!=-1){ num = countString(s.substring(si+1 , s.indexOf(")"))); num =countString(s.substring(0 , si)+num + s.substring(s.indexOf(")")+1)); }else if((si=s.replaceAll("[\\*/]", ",").indexOf(","))!= -1 ){ int statr = s.substring(0, si).replaceAll("[\\+\\-\\*/\\(\\)]", ",").lastIndexOf(",") ; System.out.println(si); int end = s.substring( si+1).replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; num = countString(s.substring(statr==-1?0:statr+1, end==-1?s.length():si+end+1)); num =countString(s.substring(0 , statr==-1?0:statr+1)+num + s.substring(end==-1?s.length():si+end+1)); }else if((si=s.replaceAll("[\\+\\-]", ",").indexOf(","))!= -1 ){ if(si==0){ num = countString("&"+s.substring(1) ); }else{ int statr = s.substring(0, si).replaceAll("[\\+\\-\\*/\\(\\)]", ",").lastIndexOf(",") ; int end = s.substring( si+1).replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; num = countString(s.substring(statr==-1?0:statr+1, end==-1?s.length():end+2)); num = countString(s.substring(0 , statr==-1?0:statr+1)+num + s.substring(end==-1?s.length():end+2)); } } }else{ int index =s.replaceAll("[\\+\\-\\*/\\(\\)]", ",").indexOf(",") ; if(index!=-1){ String s2 = s.substring(index,index+1) ; if(ss[0].substring(0, 1).equals("&")) ss[0] ="-"+ ss[0].substring(1) ; if(s2.equals("*")) num = new Integer(ss[0]) * new Integer(ss[1]) ; if(s2.equals("/")) num = new Integer(ss[0]) / new Integer(ss[1]) ; if(s2.equals("+")) num = new Integer(ss[0]) + new Integer(ss[1]) ; if(s2.equals("-")) num = new Integer(ss[0]) - new Integer(ss[1]) ; }else{ num = new Integer(s) ; } } return num; }