NJUST 喵助理照夜景

来源：互联网发布：sql入门视频教程编辑：程序博客网时间：2024/04/27 17:35

线段树+扫描线.

终于把扫描线给搞懂了.

#include <iostream>#include <cstdio>#include <algorithm>#include <memory.h>using namespace std;#define lson l, m, rt << 1#define rson m + 1, r, rt << 1 | 1const int maxn = 100010;struct seg{int p, h, f;seg(int a = 0, int b = 0, int c = 0):p(a), h(b), f(c){}bool operator<(const seg & rhs)const{return p < rhs.p;}}ss[maxn + 1000];int segs[1010 << 2], cover[1010 << 2],N;void build(int l, int r, int rt){segs[rt] = cover[rt] =0;if(l == r)return;int m = (l + r) >> 1;build(lson), build(rson);}inline void pushUp(int l, int r,int rt){if(cover[rt] > 0){//被覆盖segs[rt] = (r - l + 1);}else if(l == r){//没有被覆盖并且是原线段segs[rt] = 0;}else{//即没被覆盖也不是原线段,那么就是左右两个儿子被覆盖的长度的和segs[rt] = segs[rt << 1] + segs[rt << 1 | 1];}}void update(int v ,int L, int R, int l, int r, int rt){if(L <= l && r <= R){cover[rt] += v;pushUp(l, r, rt);return ;}int m = (l + r) >> 1;if(L <= m)update(v, L, R, lson);if(R > m) update(v, L, R, rson);pushUp(l, r, rt);}int main(){while(~scanf("%d", &N)){int maxh = 0, i, m = 0, ans = 0;for(i = 0; i < N; ++ i){int l, r, v;scanf("%d%d%d", &l, &r, &v);maxh = max(maxh, v);ss[m++] = seg(l, v, 1);ss[m++] = seg(r, v, -1);}sort(ss, ss + m);build(1, maxh, 1);for (int i = 0; i < m - 1; ++i){update(ss[i].f, 1, ss[i].h, 1, maxh, 1);ans += segs[1] * (ss[i + 1].p - ss[i].p);}printf("%d\n", ans);}return 0;}