add problem 8 add test function

Author: supercoderhawk

C/1-50/8-String-to-Integer-atoi.c

@@ -0,0 +1,77 @@
+/*
+ * Implement atoi to convert a string to an integer.
+ *
+ * Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.
+ *
+ * Notes: It is intended for this problem to be specified vaguely (ie, no given input specs). You are responsible to gather all the input requirements up front.
+ * Created by supercoderhawk on 2017/7/23.
+ */
+#include 
+#include 
+
+int myAtoi(char* str) {
+    char* tmp = str;
+    int length = 0, negative = 0,digit = 0;
+    long long result = 0, preResult = 0;
+    while (*tmp != '\0')
+    {
+        length ++;
+        tmp++;
+    }
+
+    // 处理开头空格
+    while(str[0] == ' ')
+    {
+        str ++;
+        length -- ;
+    }
+    if (length == 0)
+        return 0;
+
+    // 处理正负
+    if(str[0] == '-')
+        negative = 1;
+    if(str[0] == '-' || str[0] == '+')
+    {
+        str ++;
+        length --;
+    }
+
+    for(int i = 0; i < length; i++)
+    {
+        digit = (int)str[i];
+        if( digit>= 0x30 && digit <= 0x39){
+            preResult = result;
+            result = result*10+digit-0x30;
+            if(result<0 || preResult > result)
+                if(negative)
+                    return INT_MIN;
+                else
+                    return INT_MAX;
+        }
+        else{
+            if(negative)
+                result*= -1;
+            if(result > INT_MAX )
+                return INT_MAX;
+            if (result < INT_MIN)
+                return INT_MIN;
+            return (int)result;
+        }
+    }
+    if(negative)
+        result*= -1;
+    if(result > INT_MAX )
+        return INT_MAX;
+    if (result < INT_MIN)
+        return INT_MIN;
+    return (int)result;
+}
+
+void testMyAtoi()
+{
+    // printf("%d\n",myAtoi("   -0012a12"));
+    // printf("%d\n",myAtoi("9223372036854775809"));
+    printf("%d\n",myAtoi("18446744073709551617"));
+    printf("%d\n",myAtoi("1"));
+}