Commit 28dee28

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postfix-expression evaluation problem

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	`1`	`+/**`
	`2`	`+ * Evaluation of Postfix Expression`
	`3`	`+ * Input:456*+`
	`4`	`+ * Output:34`
	`5`	`+ */`
	`6`	`+`
	`7`	`+const Stack = require('../index');`
	`8`	`+`
	`9`	`+function evaluatePostfixExpression(expression) {`
	`10`	`+ let s = new Stack();`
	`11`	`+ for (let i = 0; i < expression.length; i++) {`
	`12`	`+ const char = expression[i];`
	`13`	`+ if (!isNaN(char)) {`
	`14`	`+ //if number push the char onto stack`
	`15`	`+ s.push(Number(char));`
	`16`	`+ } else {`
	`17`	`+ // if char is an operator then pop two elements from stack, evaluate them accordingly based on operator.`
	`18`	`+ //push the result to stack`
	`19`	`+ let val1 = s.pop();`
	`20`	`+ let val2 = s.pop()`
	`21`	`+ switch (char) {`
	`22`	`+ case '+':`
	`23`	`+ s.push(val2 + val1);`
	`24`	`+ break;`
	`25`	`+ case '-':`
	`26`	`+ s.push(val2 - val1);`
	`27`	`+ break;`
	`28`	`+ case '*':`
	`29`	`+ s.push(val2 * val1);`
	`30`	`+ break;`
	`31`	`+ case '/':`
	`32`	`+ s.push(val2 / val1);`
	`33`	`+ break;`
	`34`	`+`
	`35`	`+ }`
	`36`	`+ }`
	`37`	`+ }`
	`38`	`+ //pop the value of postfix expression`
	`39`	`+ return s.pop();`
	`40`	`+}`
	`41`	`+`
	`42`	`+console.log(evaluatePostfixExpression("123+*8-")); // -3`
	`43`	`+`
	`44`	`+console.log(evaluatePostfixExpression("12345++")); // 47`

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