Added solution for 2437

Author: chirag64

02437. Number of Valid Clock Times.rs

@@ -0,0 +1,40 @@
+impl Solution {
+    // Create 4 vars: h1, h2, m1, m2 & initialize 'output' by 1. Then based on every possible combination of whether h1 & h2 are present, multiply the 'output' accordingly. Repeat the same with m1 & m2
+    pub fn count_time(time: String) -> i32 {
+        let mut output = 1;
+        let h1 = time.chars().nth(0).unwrap();
+        let h2 = time.chars().nth(1).unwrap();
+        let m1 = time.chars().nth(3).unwrap();
+        let m2 = time.chars().nth(4).unwrap();
+        
+        // ??:xx
+        if h1 == '?' && h2 == '?' {
+            output *= 24;
+        // ?3:xx
+        } else if (h1 == '?' && (h2 as i32 - '0' as i32) < 4) {
+            output *= 3;
+        // ?9:xx
+        } else if h1 == '?' {
+            output *= 2;
+        // 1?:xx
+        } else if ((h1 as i32 - '0' as i32) < 2) && (h2 == '?') {
+            output *= 10;
+        // 2?:xx
+        } else if ((h1 as i32 - '0' as i32) == 2) && (h2 == '?') {
+            output *= 4;
+        }
+        
+        // xx:??
+        if m1 == '?' && m2 == '?' {
+            output *= 60;
+        // xx:?9
+        } else if m1 == '?' {
+            output *= 6;
+        // xx:5?
+        } else if m2 == '?' {
+            output *= 10;
+        }
+        
+        return output;
+    }
+}