ABC 047, finished b and c

atcoder/beginner_contests/abc047/src/bin/c.rs

@@ -1,5 +1,33 @@
 use proconio::input;
 
 fn main() {
-    todo!();
+    input!{
+        s: String,
+    };
+
+    let mut result = 0;
+    let mut white_segment;
+
+    let first = s.chars().next().unwrap();
+    if first == 'W' {
+        white_segment = true;
+    } else {
+        white_segment = false;
+    }
+
+    for c in s.chars() {
+        match c {
+            'W' => if !white_segment {
+                white_segment = true;
+                result += 1;
+            },
+            'B' => if white_segment {
+                result += 1;
+                white_segment = false;
+            },
+            _ => (),
+        }
+    }
+
+    println!("{}", result);
 }