题目大意：往一面墙上贴与墙等高的海报，n次贴完后，求可以看见的海报总数（看见一部分也算）
思路：明显的区间维护，用线段树，不过裸的线段树超时超空间，可以把坐标离散，得到不超过200000个有效点，每个点都表示一个小区间（a[i]~a[i+1]这一段），然后就可以轻松地解决了。不过题目有个坑，给定的右坐标其实不是实际坐标，还要+1，区间总数等于有效点数 -1,更新的时候把查找到的右端点-1再代入，具体见代码：
1 /**********************************************
2 *** Problem:
3 *** Author: JKL
4 *** University: CSUST
5 *** Team: __Dream
6 *** Email: [email protected]
7 *** My Blog: http://www.cnblogs.com/jklongint/
8 ***********************************************/
9 //===================================================
10 #include <iostream>
11 #include <fstream>
12 #include <sstream>
13 #include <iomanip>
14 #include <cstdio>
15 #include <cstdlib>
16 #include <cmath>
17 #include <cassert>
18 #include <numeric>
19 #include <ctime>
20 #include <algorithm>
21 #include <cstring>
22 #include <string>
23 #include <vector>
24 #include <queue>
25 #include <map>
26 #include <stack>
27 #include <list>
28 #include <set>
29 #include <bitset>
30 #include <deque>
31 using namespace std;
32 //---------------------------------------------------
33 #define mem(a,b) memset(a,b,sizeof(a))
34 #define GO cout<<"HelloWorld!"<<endl
35 #define Case(x) cout<<"Case "<<x<<":"
36 #define foru(i,n) for(int i=1; i <= n; i++)
37 #define ford(i,n) for(int i = n; i >= 1; i--)
38 #define fin freopen("input.txt","r",stdin);
39 #define fout freopen("output.txt","w",stdout)
40 #define lson l, m, rt << 1
41 #define rson m + 1, r, rt << 1 | 1
42
43 #define sqr(a) ((a)*(a))
44 #define abs(a) ((a>0)?(a):-(a))
45 #define pii pair<int,int>
46
47 #define fmax(a,b) max(a,b)
48 #define fmin(a,b) min(a,b)
49 #define fmax3(a,b,c) (fmax(a,fmax(a,b)))
50 #define fmin3(a,b,c) (fmin(a,fmin(a,b)))
51
52 #define sfi(x) scanf("%d",&x)
53 #define sfL(x) scanf("%I64d",&x)
54 #define sfc(x) scanf("%c",&x)
55 #define sfd(x) scanf("%lf",&x)
56 #define sfs(x) scanf("%s",x)
57 #define sfii(a,b) scanf("%d%d",&a,&b)
58 #define sfLL(a,b) scanf("%I64d%I64d",&a,&b)
59 #define sfcc(a,b) scanf("%c%c",&a,&b)
60 #define sfdd(a,b) scanf("%lf%lf",&a,&b)
61 #define sfss(a,b) scanf("%s%s",a,b)
62
63 #define pfi(x) printf("%d",x)
64 #define pfL(x) printf("%I64d",x)
65 #define pfs(x) printf("%s",x)
66 #define pfd(x) printf("%lf",x)
67 #define pfc(x) print("%c",x)
68 #define newLine pfs("\n")
69 #define space pfs(" ")
70
71 //--------------------------------------------------------
72 typedef long long LL;
73 typedef unsigned long long ULL;
74 typedef __int64 __LL;
75 typedef unsigned __int64 __ULL;
76
77 typedef vector<int> vi;
78 typedef vector<LL> vL;
79 typedef vector<string> vs;
80 typedef set<int> si;
81 typedef map<int,int> mii;
82 typedef map<LL,LL> mLL;
83 typedef map<string,int> msi;
84 typedef map<char,int> mci;
85 //--------------------------------------------------------
86 const int dx[4]={1,-1,0,0};
87 const int dy[4]={0,0,1,-1};
88 const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
89 const int N6=1000006;
90 const int N5=100006;
91 const int N4=10006;
92 const int N3=1006;
93 const int N2=106;
94 const int N=20009;
95 const int MOD=1000000007;
96 const LL LMAX=0x7fffffffffffffff;
97 const LL IMAX=0x3fffffff;
98 const double PI=3.14159265359;
99 //--------------------------------------------------------
100 template< class T > T gcd(T a, T b) { return (b != 0 ? gcd<T>(b, a%b) : a); }
101 template< class T > T lcm(T a, T b) { return (a / gcd<T>(a, b) * b); }
102
103 //------------------------------------------------------------
104 struct TreeNode{
105 int mark;
106 };
107 //=================================================================
108 TreeNode tree[N << 2];
109 int T, n, cnt, flag[N], x[N], y[N], a[N], b[N];
110 void PushUP(int rt)
111 {
112 int tl = tree[rt << 1].mark, tr = tree[rt << 1 | 1].mark;
113 if(tl != tr || tl == -1) tree[rt].mark = -1;
114 else tree[rt].mark = tl;
115 }
116 void PushDOWN(int rt)
117 {
118 int rl = rt << 1, rr = rt << 1 | 1;
119 if(tree[rt].mark > 0){
120 tree[rl].mark = tree[rt].mark;
121 tree[rr].mark = tree[rt].mark;
122 }
123 }
124 void build(int l, int r, int rt)
125 {
126 tree[rt].mark = 0;
127 if(l == r)return;
128 int m = (l + r) >> 1;
129 build(lson);
130 build(rson);
131 }
132 void update(int L, int R, int p, int l, int r, int rt)
133 {
134 if(L <= l && R >= r){
135 tree[rt].mark = p;
136 return;
137 }
138 int m = (l + r) >> 1;
139 PushDOWN(rt);
140 if(L <= m) update(L, R, p, lson);
141 if(R > m) update(L, R, p, rson);
142 PushUP(rt);
143 }
144 int query(int p, int l, int r, int rt)
145 {
146 if(l == r){
147 return tree[rt].mark;
148 }
149 int m = (l + r) >> 1;
150 PushDOWN(rt);
151 if(p <= m)return query(p, lson);
152 else return query(p, rson);
153 }
154 void discrete()
155 {
156 cnt = 0;
157 foru(i, n){
158 a[++cnt] = x[i];
159 a[++cnt] = y[i];
160 }
161 sort(a + 1, a + 1 + cnt);
162 int cc = 0;
163 foru(i, cnt){
164 if(a[i] != a[i - 1] || i == 1)b[++cc] = a[i];
165 }
166 cnt = cc;
167 }
168 int get(int x)
169 {
170 int l = 1, r = cnt;
171 while(l < r){
172 int m = (l + r) >> 1;
173 if(x < b[m]) r = m - 1;
174 if(x == b[m]) return m;
175 if(x > b[m]) l = m + 1;
176 }
177 return l;
178 }
179 int main()
180 {
181 //fin;//fout;//freopen("input.txt","r",stdin);
182 cin>>T;
183 while(T--){
184 cin>>n;
185 foru(i, n)sfii(x[i], y[i]),y[i]++;
186 discrete();
187 build(1, cnt - 1, 1);
188 foru(i, n){
189 int l = get(x[i]), r = get(y[i]) - 1;
190 if(r >= l)update(l, r, i, 1, cnt - 1, 1);
191 }
192 mem(flag, 0);
193 int ans = 0;
194 foru(i, cnt - 1){
195 int c = query(i, 1, cnt - 1, 1);
196 if(!flag[c] && c > 0){
197 flag[c] = 1;
198 ans++;
199 }
200 }
201 cout<<ans<<endl;
202 }
203 return 0;
204 }
POJ 2528 Mayor's posters（离散+线段树）
时间： 2024-08-03 23:29:45