refactor

9 Algorithms Job Interview/codes/4 numer/string_to_integer.c

@@ -0,0 +1,37 @@
+
+#include "stdio.h"
+#include "string.h"
+
+int string_to_integer(char *s,int length){
+
+	if (length>1)
+	{
+		return s[0]=='-'?string_to_integer(s,length-1)*10-(s[length-1]-'0'):string_to_integer(s,length-1)*10+s[length-1]-'0';
+	}else{
+		return s[0]=='-'?-1/10:s[0]-'0';
+
+	}
+}
+	
+/* 问题：
+1. s是空字符串
+2. s传参为非数字字符
+3. 超出整数所能表示范围
+*/
+
+
+int main(){
+
+	char *s = "4323";
+
+	printf("integer == %d\n",string_to_integer(s,strlen(s)) );
+	printf("integer == %d\n",string_to_integer("12342",5));
+	printf("integer == %d\n",string_to_integer("-11",3) );
+	printf("integer == %d\n",string_to_integer("-5",2) );
+	printf("integer == %d\n", string_to_integer("3",1));
+
+	printf("integer == %d\n", string_to_integer("abcd",4));
+	printf("integer == %d\n", string_to_integer("a",1));
+
+	return 0;
+}