fixed typos

snippets/postfixToInfix.md

@@ -1,32 +1,35 @@
 ### postfixToInfix
 
- This one has few errors and does not work properply
 
-```js
+``` js
 const postfixToInfix = RPN => {
   let convert = RPN.replace(/\^/g,'**').split(/\s+/g).filter(el => !/\s+/.test(el) && el !== '')
   let stack = []
   let result = []
-  let friends = {"+" : ["+","-","*","/"],"-":[],"/":["*"],"*":["/","*"],"**":["+","-","*","/"]}
+  let precedence = {null : 4 ,'**':3 ,'/' : 2,'*': 2,'+':1,'-':1 }
   convert.forEach(symbol => {
+    let stra,strb
     if(!isNaN(parseFloat(symbol)) && isFinite(symbol)){
       result.push(symbol)
+      stack.push(null)
     }
-    else if (Object.keys(friends).includes(symbol)) {
-      a = result.pop()
-      b = result.pop()
-      if(stack.length !==0){
-          if(friends[symbol].includes(stack.pop())){
-            result.push(`${b} ${symbol} ${a}`)
-            stack.push(symbol)
-          }
-          else{
-            result.push(`(${b}) ${symbol} ${a}`)
-            stack.push(symbol)
-          }
+    else if (Object.keys(precedence).includes(symbol)) {
+      let [a,b,opa,opb] = [result.pop(),result.pop(),stack.pop(),stack.pop()]
+      if(precedence[opb] < precedence[symbol]) {
+         strb = `(${b})`
       }
-      else {result.push(`${b} ${symbol} ${a}`);stack.push(symbol)}
-    }
+      else{
+         strb = `${b}`
+      }
+      if((precedence[opa] < precedence[symbol]) || ((precedence[opa] === precedence[symbol]) && ["/","-"].includes(symbol) )){
+         stra = `(${a})`
+      }
+      else {
+         stra = `${a}`
+      }
+      result.push(strb +symbol + stra)
+      stack.push(symbol)
+  }
     else throw `${symbol} is not a recognized symbol`
   })
   if(result.length === 1) return result.pop()