1.0s 内存限制：256.0MB
有n个点和m个区间，点和区间的端点全部是整数，对于点a和区间[b,c]，若a>=b且a<=c，称点a满足区间[b,c]。
求最小的点的子集，使得所有区间都被满足。
第一行两个整数n m
以下n行 每行一个整数，代表点的坐标
以下m行 每行两个整数，代表区间的范围
输出一行，最少的满足所有区间的点数，如无解输出-1。
样例输入：
5 5
2
6
3
8
7
2 5
3 4
3 3
2 7
6 9
样例输出：
2
1<=n,m<=10000
0<=点和区间的坐标<=50000
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Comparator;
public class xianduanhedian {
private static InputStream is = System.in;
public static int nextInt() {
try {
int i;
while ((i = is.read()) < 45 || i > 57) {
}
int mark = 1, temp = 0;
if (i == 45) {
mark = -1;
i = is.read();
}
while (i > 47 && i < 58) {
temp = temp * 10 + i - 48;
i = is.read();
}
return temp * mark;
} catch (IOException e) {
e.printStackTrace();
}
return -1;
}
static class Node {
public int start;
public int end;
public Node(int start, int end) {
this.start = start;
this.end = end;
}
}
public static void main(String[] args) {
int n = nextInt();
int m = nextInt();
int point[] = new int[n];
for (int i = 0; i < n; i++)
point[i] = nextInt();
Node node[] = new Node[m];
for (int i = 0; i < m; i++)
node[i] = new Node(nextInt(), nextInt());
Arrays.sort(point);
Arrays.sort(node, new Comparator<Node>() {
public int compare(Node o1, Node o2) {
return o1.end - o2.end;
}
});
int currentPoint = 0;
int count = 0;
int j = 1;
for (int i = 0; i < m; i++) {
int x = node[i].start;
int y = node[i].end;
if (x <= currentPoint)
continue;
int temp = -1;
for (j -= 1; j < n; j++) {
if (point[j] <= y) {
temp = point[j];
} else {
break;
}
}
if (temp == -1) {
count = 0;
break;
} else {
currentPoint = temp;
count++;
}
}
System.out.println(count);
}
}
