Valid number

Signed-off-by: Leo Ma <[email protected]>

065_valid_number/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test valid_number.c

065_valid_number/valid_number.c

@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+static bool isNumber(const char *s) {
+    bool point = false;
+    bool hasE = false;
+
+    //trim the space
+    while(isspace(*s)) s++;
+    //check empty 
+    if (*s == '\0' ) return false;
+    //check sign
+    if (*s=='+' || *s=='-') s++;
+
+    const char *head  = s;
+    for(; *s!='\0'; s++){
+        // if meet point
+        if ( *s == '.' ){
+            if ( hasE == true || point == true){
+                return false;
+            }
+            if ( s == head && !isdigit(*(s+1))  ){
+                return false;
+            }
+            point = true; 
+            continue; 
+        }
+        //if meet "e"
+        if ( *s == 'e' ){
+            if ( hasE == true || s == head) {
+                return false;
+            }
+            s++;
+            if ( *s=='+' || *s=='-' )  s++;
+            if ( !isdigit(*s) ) return false;
+
+            hasE = true; 
+            continue; 
+        }
+        //if meet space, check the rest chars are space or not
+        if (isspace(*s)){
+            for (; *s != '\0'; s++){
+                if (!isspace(*s)) return false;
+            }
+            return true;
+        }
+        if ( !isdigit(*s) ) {
+            return false;
+        }
+
+    }
+
+    return true; 
+}
+
+int main(int argc, char** argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test number\n");
+        exit(-1);
+    }
+    printf("%s\n", isNumber(argv[1]) ? "true" : "false");
+    return 0;
+}