Create 224.Basic Calculator.cpp

wisdompeak · web-flow · commit b523b247d68b · 2017-06-27T13:31:52.000-05:00
diff --git a/Stack/224.Basic-Calculator/224.Basic Calculator.cpp b/Stack/224.Basic-Calculator/224.Basic Calculator.cpp
@@ -0,0 +1,44 @@
+class Solution {
+public:
+    int calculate(string s) 
+    {
+        stack<int>nums;
+        stack<int>sign;
+        s.insert(s.begin(),'+');
+        
+        int curResult=0;
+        for (int i=0; i<s.size(); i++)
+        {
+            if (s[i]=='(')
+            {
+                nums.push(curResult);
+                curResult=0;
+                sign.push(1);
+            }
+            else if (s[i]==')')
+            {
+                curResult*=sign.top();
+                sign.pop();
+                curResult+=nums.top();
+                nums.pop();
+            }
+            else if (s[i]=='+')
+                sign.push(1);
+            else if (s[i]=='-')
+                sign.push(-1);
+            else if (s[i]>='0' && s[i]<='9')
+            {
+                int i0=i;
+                while (i<s.size() && s[i]>='0' && s[i]<='9')
+                    i++;
+                int num = stoi(s.substr(i0,i-i0));
+                curResult+=sign.top()*num;
+                sign.pop();
+                i--;
+            }
+        }
+        
+        return curResult;
+        
+    }
+};
