3

Author: kedebug

ValidNumber/ValidNumber.cpp

@@ -0,0 +1,43 @@
+class Solution {
+public:
+    bool isNumber(const char *s) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        while (*s != '\0' && *s == ' ') s += 1;
+        if (*s == '\0') return false;
+        
+        const char *e = s + strlen(s) - 1;
+        while (s <= e && *e == ' ')  e -= 1;
+        
+        bool is_digit = false;
+        bool has_dot = false;
+        bool has_exp = false;
+        
+        if (*s == '+' || *s == '-') s += 1;
+        
+        while (s <= e) {
+            if ('0' <= *s && *s <= '9') {
+                is_digit = true;
+            }
+            else if (*s == '.') {
+                if (has_dot || has_exp)
+                    return false;
+                has_dot = true;
+            }
+            else if (*s == 'e') {
+                if (!is_digit || has_exp)
+                    return false;
+                has_exp = true;
+                is_digit = false;
+            }
+            else if (*s == '+' || *s == '-') {
+                if (*(s-1) != 'e')
+                    return false;
+            }
+            else return false;
+            s += 1;
+        }
+        return is_digit;
+    }
+};