Leetcode day 2 and 3

leetcode/lc8/atoi.cpp

@@ -0,0 +1,37 @@
+class Solution {
+public:
+    int myAtoi(string s) {
+        if(s.empty()) return 0;
+        
+        const long long MAX_INT = INT_MAX;
+        const long long MIN_INT = INT_MIN;
+
+        int n = s.length();
+        int i = 0;
+        while(i<n && s[i]==' ')
+            i++;
+        if(i==n)
+            return 0;    
+        int sign = 1;
+        if(s[i]=='+')
+            i++;
+        else if(s[i]== '-'){
+            sign = -1;
+            i++;
+        }
+
+        long long res= 0;
+        while(i<n && isdigit(s[i])){
+            int digit = s[i] - '0';
+            res = res*10 + digit;
+
+            if(sign*res >= MAX_INT)
+                return MAX_INT;
+            if(sign*res <= MIN_INT)
+                return MIN_INT;
+            i++;        
+        }  
+        return sign*res;     
+    }
+
+};