HDU 5124 lines（BestCoder Round #20）

#include<stdio.h>
#include<string.h>
#include<queue>
#include<math.h>
#include<stdlib.h>
#include<algorithm>
using namespace std;

const int N=1e6+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;

typedef long long LL;

int a[N], b[N];
int c[N];
int vis[N];

int main ()
{
    int T, n, i;

    scanf("%d", &T);

    while (T--)
    {
        scanf("%d", &n);

        memset(vis, 0, sizeof(vis));

        for (i = 0; i < n; i++)
        {
            scanf("%d%d", &a[i], &b[i]);
            
            c[i] = a[i];
            c[i+n] = b[i];
        }

        sort(c, c+2*n);

        for (i = 0; i < n; i++)
        {
            int indexa = lower_bound(c, c+2*n, a[i]) - c; ///在c数组中找到第一个>=a[i]的位置（该位置就是离散化后的a[i]）
            int indexb = lower_bound(c, c+2*n, b[i]) - c;

            vis[indexa]++;
            vis[indexb+1]--;
        }

        int ans = 0, Max = -INF;

        for (i = 0; i < 2*n; i++)
        {
            ans += vis[i];
            if (ans > Max) Max = ans;
        }

        printf("%d\n", Max);
    }

    return 0;
}