第二题 import java.util.Scanner; public class t2 { public static void main(String[] args) { Scanner scanner=new Scanner(System.in); String N= scanner.nextLine(); int n=Integer.valueOf(N); String[][] luxian=new String[n][]; for (int i=0;i<n;i++){ String in=scanner.nextLine(); luxian[i]=in.split(" "); } int time=0; String start=luxian[0][0]; for (int i=0;i<n;i++){ for (int j=0;j<2;j++){ if (luxian[i][j].equals(start)&&j==1){ time++; if (i<n-1) { start = luxian[i + 1][0]; } } } } System.out.print(time); } }