【线段树】 POJ 3277 City Horizon 裸扫描线

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <string>
#include <iostream>
#include <algorithm>
#include <sstream>
using namespace std;
#include <queue>
#include <stack>
#include <vector>
#include <deque>
#include <set>
#include <map>
#define cler(arr, val)    memset(arr, val, sizeof(arr))
#define IN     freopen ("in.txt" , "r" , stdin);
#define OUT  freopen ("out.txt" , "w" , stdout);
typedef long long  LL;
const int MAXN = 1000006;//点数的最大值
const int MAXM = 20006;//边数的最大值
const int INF = 11521204;
const int mod=1000000007;
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
const int maxn = 84444;
int cnt[maxn << 2];
int sum[maxn << 2];
int X[maxn];
struct Seg
{
int h , l , r;
int s;
Seg() {}
Seg(int a,int b,int c,int d) : l(a) , r(b) , h(c) , s(d) {}
bool operator < (const Seg &cmp) const
{
return h < cmp.h;
}
} ss[maxn];
void PushUp(int rt,int l,int r)
{
if (cnt[rt]) sum[rt] = X[r+1] - X[l];
else if (l == r) sum[rt] = 0;
else sum[rt] = sum[rt<<1] + sum[rt<<1|1];
}
void update(int L,int R,int c,int l,int r,int rt)
{
if (L <= l && r <= R)
{
cnt[rt] += c;
PushUp(rt , l , r);
return ;
}
int m = (l + r) >> 1;
if (L <= m) update(L , R , c , lson);
if (m < R) update(L , R , c , rson);
PushUp(rt , l , r);
}
int Bin(int key,int n,int X[])
{
int l = 0 , r = n - 1;
while (l <= r)
{
int m = (l + r) >> 1;
if (X[m] == key) return m;
if (X[m] < key) l = m + 1;
else r = m - 1;
}
return -1;
}
int main()
{
int n ;
// IN;
while (scanf("%d",&n)!=EOF)
{
int m = 0;
while (n --)
{
int x,y,z,o=0;
scanf("%d%d%d",&x,&y,&z);
X[m] = x;
ss[m++] = Seg(x , y , o , 1);
X[m] = y;
ss[m++] = Seg(x , y , z , -1);
}
sort(X , X + m);
sort(ss , ss + m);
int k = 1;
for (int i = 1 ; i < m ; i ++)
{
if (X[i] != X[i-1]) X[k++] = X[i];
}
memset(cnt , 0 , sizeof(cnt));
memset(sum , 0 , sizeof(sum));
LL ret = 0;
for (int i = 0 ; i < m - 1 ; i ++)
{
int l = Bin(ss[i].l , k , X);
int r = Bin(ss[i].r , k , X) - 1;
if (l <= r) update(l , r , ss[i].s , 0 , k - 1, 1);
ret +=(LL)sum[1] * (ss[i+1].h - ss[i].h);
}
printf("%I64d\n", ret);
}
return 0;
}