3427 : 볼 모으기(balls)

import java.util.Scanner;
 
public class Main {
 
    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub 
         
        Scanner scan = new Scanner(System.in);
         
        int n;
        String arr;
        int i, j;
         
        n = scan.nextInt();
         
         
        arr= scan.next();
         
         
        int red = 0, blue = 0;
        int rs = 0, bs = 0;
        int re=0,be=0;
         
        for (i = 0; i < n; i++) {
            if (arr.charAt(i) == 'R') {
                red++;
            }
            else {
                blue++;
            }
        }
         
       for (i = 0; i < n; i++) {
           if (i == 0 && arr.charAt(i)== 'R') {
               rs = 1;
           }
           else if (i == 0 && arr.charAt(i) == 'B') {
               bs = 1;
           }
           else {
               if (arr.charAt(i - 1) != arr.charAt(i)) {
                   break;
               }
               if (arr.charAt(i) == 'R') {
                   rs++;
               }
               else {
                   bs++;
               }
           }
       }
        
        
       for (i = n-1; i >= 0; i--) {
           if (arr.charAt(i) == 'R' && i == n - 1) {
               re = 1;
           }
           else if (arr.charAt(i) == 'B' && i == n - 1) {
               be = 1;
           }
           else {
               if (arr.charAt(i + 1) != arr.charAt(i)) {
                   break;
               }
               if (arr.charAt(i) == 'R') {
                   re++;
               }
               else {
                   be++;
               }
           }
       }
 
       int val = red - rs;
       val = Math.min(val, red - re);
       val = Math.min(val, blue - bs);
       val = Math.min(val, blue - be);
        
      
       System.out.printf("%d", val);
    }
 
}

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