# Algorithm Sedgewick Fourth Edition-1th Chapter Foundation-201 evaluates the value of an expression by priority

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`1 /******************************************************************************2 * Compilation:javac Evaluatedeluxe.java3 * Execution:java Evaluatedeluxe4 * Dependencies:Stack.java5  *6 * evaluates arithmetic expressions using Dijkstra ' s two-stack algorithm.7 * Handles The following binary operators: +,-, *,/and parentheses.8  *9 *% echo "3 + 5 * 6-7 * (8 + 5)" | java evaluatedeluxeTen * -58.0 One  * A  * - * Limitiations -  *  -------------- the *-can easily add additional operators and precedence orders, but they - * Must be left associative (exponentiation are right associative) - *-assumes whitespace between operators (including parentheses) -  * + * Remarks -  *  -------------- + *-can eliminate second phase if we enclose input expression A * in parentheses (and, then, could also remove the test at * For whether the operator stack was empty in the inner while loop) - *- Seehttp://introcs.cs.princeton.edu/java/11precedence/ for - * operator Precedence in Java -  * -  ******************************************************************************/ -  in ImportJava.util.TreeMap; -  to  Public classEvaluatedeluxe { +  -     //result of applying binary operator op to operands val1 and Val2 the      Public Static DoubleEval (String op,DoubleVal1,Doubleval2) { *         if(Op.equals ("+"))returnVal1 +Val2; \$         if(Op.equals ("-"))returnVal1-Val2;Panax Notoginseng         if(Op.equals ("/"))returnVAL1/Val2; -         if(Op.equals ("*"))returnVAL1 *Val2; the         Throw NewRuntimeException ("Invalid operator"); +     } A  the      Public Static voidMain (string[] args) { +  -         //precedence order of operators \$Treemap<string, integer> precedence =NewTreemap<string, integer>(); \$Precedence.put ("(", 0);//For convenience with algorithm -Precedence.put (")", 0);  -Precedence.put ("+", 1);//+ and-have Lower precedence than * and/ thePrecedence.put ("-", 1); -Precedence.put ("*", 2);WuyiPrecedence.put ("/", 2); the  -stack<string> Ops =NewStack<string>(); WuStack<double> Vals =NewStack<double>(); -  About          while(!Stdin.isempty ()) { \$  -             //read in next token (operator or value) -String s =stdin.readstring (); -  A             //token is a value +             if(!Precedence.containskey (s)) { the Vals.push (double.parsedouble (s)); -                 Continue; \$             } the  the             //Token is an operator the              while(true) { the  -                 //The last condition ensures, the operator with higher precedence is evaluated first in                 if(Ops.isempty () | | s.equals ("(") | | (Precedence.get (s) >Precedence.get (Ops.peek ()))) { the Ops.push (s); the                      Break; About                 } the  the                 //Evaluate Expression theString op =Ops.pop (); +  -                 //But ignore left parentheses the                 if(Op.equals ("(")) {Bayi                     assertS.equals (")"); the                      Break; the                 } -  -                 //evaluate operator and operands and push result onto value stack the                 Else { the                     DoubleVal2 =Vals.pop (); the                     DoubleVal1 =Vals.pop (); the Vals.push (eval (OP, Val1, Val2)); -                 } the             } the         } the 94         //finished parsing string-evaluate operator and operands remaining on both stacks the          while(!Ops.isempty ()) { theString op =Ops.pop (); the             DoubleVal2 =Vals.pop ();98             DoubleVal1 =Vals.pop (); About Vals.push (eval (OP, Val1, Val2)); -         }101 102         //Last value in stack is value of expression103 stdout.println (Vals.pop ());104         assertvals.isempty (); the         assertops.isempty ();106     }107}`

Algorithm Sedgewick Fourth Edition-1th Chapter Foundation-201 evaluates the value of an expression by priority

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