Merge pull request #7 from CodeB9/master

Add nested brackets algorithm

Author: dynamitechetan

nested_brackets.go

@@ -0,0 +1,54 @@
+// The nested brackets problem is a problem that determines if a sequence of
+// brackets are properly nested.  A sequence of brackets s is considered properly nested
+// if any of the following conditions are true:
+// 	- s is empty
+// 	- s has the form (U) or [U] or {U} where U is a properly nested string
+// 	- s has the form VW where V and W are properly nested strings
+// For example, the string "()()[()]" is properly nested but "[(()]" is not.
+// The function called isBalanced takes as input a string which is a sequence of brackets and
+// returns true if input is nested and false otherwise.
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func isBalanced(input string) string {
+
+	if len(input) > 0 {
+		var stack []byte
+		for i := 0; i < len(input); i++ {
+			if input[i] == '(' || input[i] == '{' || input[i] == '[' {
+				stack = append(stack, input[i])
+			} else {
+				if len(stack) > 0 {
+					pair := string(stack[len(stack)-1]) + string(input[i])
+					stack = stack[:len(stack)-1]
+
+					if pair != "[]" && pair != "{}" && pair != "()" {
+						return input + " is not balanced."
+					}
+				} else {
+					return input + " is not balanced."
+				}
+			}
+		}
+		if len(stack) == 0 {
+			return input + " is balanced."
+		}
+	}
+	return "Please enter a sequence of brackets."
+}
+
+func main() {
+	reader := bufio.NewReader(os.Stdin)
+	fmt.Print("Enter sequence of brackets: ")
+	text, _ := reader.ReadString('\n')
+
+	text = strings.TrimSpace(text)
+	fmt.Println(isBalanced(text))
+}