C的写法，使用了qsort进行排序,也因此需要写出相应的比较函数

#include <stdio.h>
#include <stdlib.h>

typedef struct Activity{
    int start;
    int end;
} Activity;

Activity activity[10000];


int n;
int ans;

void init() {
    int s,e;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%d %d", &s, &e);
        activity[i].start = s;
        activity[i].end = e;
    }
}

int cmp(const void *a, const void *b) {
    Activity *x = (Activity *)a;
    Activity *y = (Activity *)b;
    if (x->end == y->end) {
        return x->start - y->start;
    } else {
        return x->end - y->end;
    }
}

void solve() {
    qsort(activity, n, sizeof(Activity), cmp);

    ans = 1;
    int last = activity[0].end;

    for (int i = 1; i < n; i++) {
        if (activity[i].start >= last + 1) {
            ans++;
            last = activity[i].end;
        }
    }
    printf("%d\n", ans);
}


int main() {
    int m;
    scanf("%d", &m);

    for (int i = 0; i < m; i++) {
        init();
        solve();
    }

    return 0;
}

以下为qsort函数原型

void qsort(
    void *base,        // 待排序数组的首地址（任意类型指针）
    size_t nmemb,      // 数组中元素的个数
    size_t size,       // 每个元素的大小（单位：字节）
    int (*compar)(const void *, const void *)  // 比较函数指针
);