zoj 3518 Unsafe Factor

#include <queue>
#include <stack>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <limits.h>
#include <string.h>
#include <string>
#include <algorithm>

using namespace std;

const int MAX = 10000010;
const int N = 400010;
struct LL{ int x,y,c;};
LL b
;
int a
;
bool col[MAX];
bool ans[MAX];
int mmax;
void solve(int n,int cnt,int nn)
{
	for(int i=0; i<n; i++)
	{
		int x = lower_bound(a,a+cnt,b[i].x) - a;
		int y = lower_bound(a,a+cnt,b[i].y) - a;
		for(int k=x; k<y; k++)
		{
			if( col[k] == true )
				col[k] = false;
			else
				col[k] = true;
		}
	}
	for(int i=0; i<cnt-1; i++)
		if( col[i] )
		{
			for(int k=a[i]; k<a[i+1]; k++)
				ans[k] = true;
		}
	int sum = 0;
	mmax = 0;
	for(int i=0; i<nn+1; i++)
		if( ans[i] )
			sum++;
		else
		{
			if( sum > mmax ) mmax = sum;
			sum = 0;
		}
	if( sum > mmax ) mmax = sum;
}

int main()
{
	int n,cnt,n1,n2;
	
	while( ~scanf("%d",&n) )
	{
		memset(ans,false,sizeof(ans));
		memset(col,false,sizeof(col));
		cnt = 0;
		scanf("%d%d",&n1,&n2);
		for(int i=0; i<n1+n2; i++)
		{
			scanf("%d%d",&b[i].x,&b[i].y);
			b[i].y++;
			a[cnt++] = b[i].x; a[cnt++] = b[i].y;
		}
		sort(a,a+cnt);
		cnt = unique(a,a+cnt) - a;
		solve(n1+n2,cnt,n);
		if( mmax == 0 )
			printf("0\n");
		else
			printf("%d\n",mmax);
	}
return 0;
}