Solution to #issue pezy#23 : String to Integer (atoi) is not found (404)

Have not added any Readme file since Readme files are in different language.
Since main Readme file doesn't contain this problem, I have labeled it as 711.

711. String to Integer (atoi)/solution.h

@@ -0,0 +1,65 @@
+class Solution {
+public:
+    bool isOverflow(long long a, long long b){
+        long long res=a*10+b-48;
+        if(res>INT_MAX)
+            return true;
+        return false;
+    }
+
+    int myAtoi(string s) {
+        int c=0;
+        bool isminus=0;
+        bool nostart=0;
+        for(int i=0;i<s.size();i++){
+
+            if(s[i]==32){
+                if(!nostart)
+                    continue;
+                else
+                    break;
+            }
+            else if(s[i]==43){
+                if(!nostart)
+                    nostart=1;
+                else
+                    break;
+            }
+            else if(s[i]==45){
+                if(nostart)
+                    break;
+                else{
+                    isminus=1;
+                    nostart=1;
+                }
+            }
+            else if((s[i]<48)||s[i]>57){
+                break;
+            }
+            else{
+                nostart=1;
+                if(isOverflow(c,s[i])){ 
+                    if(isminus){
+                        c=INT_MIN;
+                        isminus=0;
+                    }
+                    else{
+                        c=INT_MAX;
+                    }
+                    break;
+                }
+
+                else{
+                    c=c*10+(s[i]-48);
+                }
+
+            }
+        }
+
+        if(isminus){
+            c=c*-1;
+        }
+
+        return c;
+    }
+};