Equalize.java

/**
 * http://codeforces.com/problemset/problem/1037/C #dynamic-programming #greedy 2 lien ke => nen
 * swap (vi cost flip = 2, cost swap = 1)
 */
import java.util.Scanner;

public class Equalize {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    String a = sc.next();
    String b = sc.next();

    int preChangePos = -2;
    int cost = 0;
    for (int i = 0; i < n; i++) {
      if (a.charAt(i) != b.charAt(i)) {
        // swap
        if (preChangePos == i - 1 && a.charAt(i) != a.charAt(i - 1)) {
          // reset
          preChangePos = -2;
        } else { // flip
          cost++;
          // update previous change position
          preChangePos = i;
        }
      }
    }
    /**
     * clear way int i = 0; while (i < n) { if (a.charAt(i) != b.charAt(i)) { if (i+1 < n &&
     * a.charAt(i+1) != b.charAt(i+1) && a.charAt(i+1) != a.charAt(i)) { // swap cost++; i += 2; }
     * else { // flip cost++; i++; } } else { i++; } }
     */
    System.out.println(cost);
  }
}