Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        String S = sc.next();

        int[] blackcount = new int[N];
        int bkl = 0;
        for (int i = 0; i<N; i++) {
            if (S.charAt(i)== '#') bkl++;
            blackcount[i] = bkl;
        }
        int blackall = blackcount[N-1];
        int count = N;
        for (int i = 0; i < N; i++) {
            int leftchange = blackcount[i];
            int rightchange = (N-1-i-(blackall-leftchange));
            count = Math.min(count,(leftchange+rightchange));
        }
        System.out.println(count);
    }
}