import java.util.Scanner;
public class Main{
    public static void main(String args[]) {
        Scanner input = new Scanner(System.in);
        int N = input.nextInt();
        int T = input.nextInt();
        int[] intervals = new int[T + 1];  //下标代表开始时间,值代表结束时间,如果值为0,代表没有以下标为开始的段
        int num = N;
        int maxStart = -1;
        while ((--num) >= 0) {
            int s = input.nextInt();
            int e = input.nextInt();
            maxStart = Math.max(maxStart, s);
            if(e > intervals[s] && e >= s){
                intervals[s] = e;
            }
        }
        if (intervals[1] < 1 || intervals[maxStart] < T) {
            System.out.println(-1);
            return;
        }
        int count = 1;  //计算总共需要多少牛
        int i = 1;
        int e = intervals[i];
        while (++i <= T) {
            if (e >= T) {  //已覆盖所有时间段,退出
                break;
            }
            int newE = 0;
            while (i <= T && i <= (e + 1)) {
                if (intervals[i] > newE) {
                    newE = intervals[i];
                }
                i++;
            }
            i--;
            if (newE == 0) { //中间有断裂情况
                count = -1;
                break;
            } else {
                e = newE;
                count++;
            }
        }
        if (e >= T) {
            System.out.println(count);
        } else {
            System.out.println(-1);
        }
    }
}

• Re:Discuss区中的所有测试用例全过,但是仍然WA,求大神指点迷津! (1597) qw885 2018-03-14 12:56:06