[CF707D]Persistent Bookcase(离线,DFS)

题目链接:http://codeforces.com/contest/707/problem/D

题意:维护一个图,一共四个操作。

1.第i行第j列变1

2.第i行第j列变0

3.第i行颠倒,1变0,0变1

4.将整张图变为k次操作时的状态如果k是0的话,则清空图

乍一看就知道可以用bitset来保存图,但是更新图的话复杂度太高,纯模拟一定会TLE。所以可以离线做,存下所有状态。并且根据操作建树,假如j操作是i次操作的下一步,则将j操作作为i的儿子,1~3操作都是i-1作为i的父亲,只有4操作特殊,设i是k的儿子。这里树根设0,0存一个空的图就解决操作4的操作数是0的问题了。之后回溯每次查询,查询完一条后回溯到前一状态走另外的儿子就行了。

  1 /*
  2 ━━━━━┒ギリギリ♂ eye!
  3 ┓┏┓┏┓┃キリキリ♂ mind!
  4 ┛┗┛┗┛┃\○/
  5 ┓┏┓┏┓┃ /
  6 ┛┗┛┗┛┃ノ)
  7 ┓┏┓┏┓┃
  8 ┛┗┛┗┛┃
  9 ┓┏┓┏┓┃
 10 ┛┗┛┗┛┃
 11 ┓┏┓┏┓┃
 12 ┛┗┛┗┛┃
 13 ┓┏┓┏┓┃
 14 ┃┃┃┃┃┃
 15 ┻┻┻┻┻┻
 16 */
 17 #include <algorithm>
 18 #include <iostream>
 19 #include <iomanip>
 20 #include <cstring>
 21 #include <climits>
 22 #include <complex>
 23 #include <fstream>
 24 #include <cassert>
 25 #include <cstdio>
 26 #include <bitset>
 27 #include <vector>
 28 #include <deque>
 29 #include <queue>
 30 #include <stack>
 31 #include <ctime>
 32 #include <set>
 33 #include <map>
 34 #include <cmath>
 35 using namespace std;
 36 #define fr first
 37 #define sc second
 38 #define cl clear
 39 #define BUG puts("here!!!")
 40 #define W(a) while(a--)
 41 #define pb(a) push_back(a)
 42 #define Rint(a) scanf("%d", &a)
 43 #define Rll(a) scanf("%I64d", &a)
 44 #define Rs(a) scanf("%s", a)
 45 #define Cin(a) cin >> a
 46 #define FRead() freopen("in", "r", stdin)
 47 #define FWrite() freopen("out", "w", stdout)
 48 #define Rep(i, len) for(int i = 0; i < (len); i++)
 49 #define For(i, a, len) for(int i = (a); i < (len); i++)
 50 #define Cls(a) memset((a), 0, sizeof(a))
 51 #define Clr(a, x) memset((a), (x), sizeof(a))
 52 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
 53 #define lrt rt << 1
 54 #define rrt rt << 1 | 1
 55 #define pi 3.14159265359
 56 #define RT return
 57 #define lowbit(x) x & (-x)
 58 #define onecnt(x) __builtin_popcount(x)
 59 typedef long long LL;
 60 typedef long double LD;
 61 typedef unsigned long long ULL;
 62 typedef pair<int, int> pii;
 63 typedef pair<string, int> psi;
 64 typedef pair<LL, LL> pll;
 65 typedef map<string, int> msi;
 66 typedef vector<int> vi;
 67 typedef vector<LL> vl;
 68 typedef vector<vl> vvl;
 69 typedef vector<bool> vb;
 70 
 71 typedef struct Node {
 72     int k, x, y;
 73 }Node;
 74 const int maxn = 1010;
 75 const int maxm = 100100;
 76 int ret;
 77 int q, n, m;
 78 int cmd, a, b, c;
 79 bitset<maxn> st[maxn];
 80 vi mp[maxm];
 81 Node qq[maxm];
 82 int ans[maxm];
 83 
 84 void go(int x, int& ok) {
 85     int k = qq[x].k;
 86     int i = qq[x].x;
 87     int j = qq[x].y;
 88     if(k == 1) {
 89         if(!st[i][j]) {
 90             st[i][j] = 1;
 91             ret++;
 92             ok = 1;
 93         }
 94         else ok = 0;
 95     }
 96     if(k == 2) {
 97         if(st[i][j]) {
 98             st[i][j] = 0;
 99             ret--;
100             ok = 1;
101         }
102         else ok = 0;
103     }
104     if(k == 3) {
105         int cur = st[i].count();
106         if(st[i][maxn-1] == 1) cur -= (maxn - m);
107         ret = ret - cur + (m - cur);
108         st[i] = ~st[i];
109     }
110 }
111 
112 void re(int x, int& ok) {
113     int k = qq[x].k;
114     int i = qq[x].x;
115     int j = qq[x].y;
116     if(k == 1) {
117         if(ok) {
118             st[i][j] = 0;
119             ret--;
120         }
121     }
122     if(k == 2) {
123         if(ok) {
124             st[i][j] = 1;
125             ret++;
126         }
127     }
128     if(k == 3) {
129         int cur = st[i].count();
130         if(st[i][maxn-1] == 1) cur -= (maxn - m);
131             ret = ret - cur + (m - cur);
132             st[i] = ~st[i];
133     }
134 }
135 
136 void dfs(int x) {
137     int ok;
138     if(x) {
139         go(x, ok);
140         ans[x] = ret;
141     }
142     Rep(i, mp[x].size()) dfs(mp[x][i]);
143     re(x, ok);
144 }
145 
146 int main() {
147     // FRead();
148     while(~scanf("%d%d%d",&n,&m,&q)) {
149         For(i, 1, q+1) {
150             Rint(qq[i].k);
151             if(qq[i].k <= 2) {
152                 Rint(qq[i].x);
153                 Rint(qq[i].y);
154             }
155             else Rint(qq[i].x);
156         }
157         For(i, 2, q+1) {
158             if(qq[i].k == 4) mp[qq[i].x].push_back(i);
159             else mp[i-1].push_back(i);
160         }
161         mp[0].push_back(1);
162         dfs(0);
163         For(i, 1, q+1) printf("%d
", ans[i]);
164     }
165     RT 0;
166 }
原文地址:https://www.cnblogs.com/kirai/p/5793978.html