算法

这个题目感觉很像是Leetcode里面的jump game II， 可以贪心选择区间。
链接如下：
https://leetcode.com/problems/jump-game-ii/
https://leetcode-cn.com/problems/jump-game-ii/

Java 代码

import java.util.Scanner;
import java.util.Arrays;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt(), T = in.nextInt();
        int[][] intervals = new int[n][2];
        for (int i = 0; i < n; ++i) {
            intervals[i][0] = in.nextInt();
            intervals[i][1] = in.nextInt();
        }
        in.close();
        System.out.println(minCows(n, T, intervals));
    }

    private static int minCows(int n, int T, int[][] intervals) {
        Arrays.sort(intervals, (a, b) -> Integer.compare(a[0], b[0]));
        int count = 1;
        int curRight = 0, curLeft = 1;
        for (int i = 0; i < n; ++i) {
            if (intervals[i][0] <= curLeft) {
                curRight = Math.max(curRight, intervals[i][1]);
            } else if (intervals[i][0] > curRight + 1) {
                return -1;
            } else {
                if (curRight == T) return count;
                curLeft = curRight + 1;
                curRight = Math.max(curRight, intervals[i][1]);
                count++;
            }
        }
        return curRight == T ? count : -1;
    }
}