evaluate_reverse_polish_notation

hitzzc · hitzzc · commit be7bb930e71e · 2016-10-14T11:14:50.000+08:00
diff --git a/README.md b/README.md
@@ -133,6 +133,7 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [147. insertion sort list](https://github.com/hitzzc/go-leetcode/tree/master/insertion_sort_list)
 #### [148. sort list](https://github.com/hitzzc/go-leetcode/tree/master/sort_list)
 #### [149. Max Points on a Line](https://github.com/hitzzc/go-leetcode/tree/master/max_points_on_a_line)
+#### [150. evaluate reverse polish notation](https://github.com/hitzzc/go-leetcode/tree/master/evaluate_reverse_polish_notation)
 
 
 
diff --git a/evaluate_reverse_polish_notation/evaluate_reverse_polish_notation.go b/evaluate_reverse_polish_notation/evaluate_reverse_polish_notation.go
@@ -0,0 +1,38 @@
+package evaluate_reverse_polish_notation
+
+import (
+	"strconv"
+)
+
+func evalRPN(tokens []string) int {
+	cache := []int{}
+	var num1, num2, num int
+	for i := range tokens {
+		if tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" || tokens[i] == "/" {
+			num2 = cache[len(cache)-1]
+			num1 = cache[len(cache)-2]
+			cache[len(cache)-2] = calculate(num1, num2, tokens[i])
+			cache = cache[:len(cache)-1]
+		} else {
+			num, _ = strconv.Atoi(tokens[i])
+			cache = append(cache, num)
+		}
+	}
+	return cache[0]
+}
+
+func calculate(num1, num2 int, op string) int {
+	if op == "+" {
+		return num1 + num2
+	}
+	if op == "-" {
+		return num1 - num2
+	}
+	if op == "*" {
+		return num1 * num2
+	}
+	if op == "/" {
+		return num1 / num2
+	}
+	return 0
+}
