Hello,
I am evaluating a string expression using recursion. It is not working for parenthesis, please help me.
Here is my code
// For Addition and Substraction
static int evalAS(String e) {
int p1 = e.lastIndexOf("+");
int p2 = e.lastIndexOf("-");
int p = Math.max(p1, p2);
if (p == -1)
return Integer.parseInt(e);
if (e.charAt(p) == '+')
return evalAS(e.substring(0, p))
+ Integer.parseInt(e.substring(p + 1));
return evalAS(e.substring(0, p)) - Integer.parseInt(e.substring(p + 1));
}
// For Multiplication and Division
static int evalMD(String e) {
int p1 = e.lastIndexOf("*");
int p2 = e.lastIndexOf("/");
int p = Math.max(p1, p2);
if (p == -1)
return Integer.parseInt(e);
if (e.charAt(p) == '*')
return evalMD(e.substring(0, p))
* Integer.parseInt(e.substring(p + 1));
return evalMD(e.substring(0, p)) / Integer.parseInt(e.substring(p + 1));
}
// Evaluation whole expression
static int evalE(String e) {
int s1 = e.indexOf("(");
int s2 = e.lastIndexOf(")");
if(s1 != -1 && s2!= -1)
{
// ?????
}
int p1 = e.lastIndexOf("+");
int p2 = e.lastIndexOf("-");
int p = Math.max(p1, p2);
if (p == -1)
return evalMD(e);
if (e.charAt(p) == '+')
return evalE(e.substring(0, p)) + evalMD(e.substring(p + 1));
return evalE(e.substring(0, p)) - evalMD(e.substring(p + 1));
}
I am confused, how to store and evaluate expression with sub expression.
