AOJ 0525 穷举 - 7hat - 博客园


http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=0525
题意:有一个烤饼器可以烤r行c列的煎饼,煎饼可以正面朝上(用1表示)也可以背面朝上(用0表示)。一次可将同一行或同一列的煎饼全部翻转。现在需要把尽可能多的煎饼翻成正面朝上,问最多能使多少煎饼正面朝上?
输入:多组输入,每组第一行为二整数r, c (1 ≤ r ≤ 10, 1 ≤ c ≤ 10 000),剩下r行c列表示煎饼初始状态。r=c=0表示输入结束。
输出:对于每组输入,输出最多能使多少煎饼正面朝上。
(翻译参考自:http://bbs.byr.cn/#!article/ACM_ICPC/73337?au=Milrivel)
分析:这个是二维的穷举,因为列数比较多行数比较少,所以可对行做深度优先遍历穷举所有行的情况。这里用bitset保存每一行的情况,对于行的翻装,只需要用自带的flip函数。对于每一行都确定动作时,统计每一列翻时会出现的正面朝上的值以及不翻时的值,取较大数。此时为行动作确定时,列动作可以做到的最优值。因此穷举所有行情况即可求出实际最优值。
http://www.hankcs.com/program/cpp/aoj-0525-osenbei-challenge-programming-contest-2nd-edition-exercises-answers.html
枚举的话,先从行开始,一共有2^R种翻转可能,行翻转完毕再翻转列。列的翻转不必真的flip,只需要统计一下朝上的煎饼果子和朝下的煎饼果子,两者比较取其最大值即可。
bitset<10000> cookie[10];
int main(int argc, char *argv[])
{
    int R, C;
    while(cin >> R >> C && R > 0)
    {
        int i, j;
        for (i = 0; i < R; ++i)
        {
            for (j = 0; j < C; ++j)
            {
                bool upwards;
                cin >> upwards;
                cookie[i][j] = upwards;
            }
        }
        // 在横向一共有2^R种变换
        int permute_r = 1 << R;
        int result = 0;
        for (i = 0; i < permute_r ; ++i)
        {
            // 完成当前的变换
            for (j = 0; j < R; ++j)
            {
                // 这一行是否应当翻个面
                if (i & (1 << j))
                {
                    cookie[j].flip();
                }
            }
            // 对每一列分别算出朝上和朝下的煎饼个数,取其最大值
            int possible_answer = 0;
            for (j = 0; j < C; ++j)
            {
                int up_cookie_count = 0;
                for (int k = 0; k < R; ++k)
                {
                    if (cookie[k][j])
                    {
                        ++up_cookie_count;
                    }
                }
                possible_answer += max(up_cookie_count, R - up_cookie_count);
            }
            // 结果取最大值
            result = max(result, possible_answer);
             
            // 复原
            for (j = 0; j < R; ++j)
            {
                if (i & (1 << j))
                {
                    cookie[j].flip();
                }
            }
        }
        cout << result << endl;
    }
    return 0;
}
http://www.cnblogs.com/7hat/p/3605315.html
int R, C;
12 bitset<MAX_C> a[MAX_R];
14 int ans;
16 void dfs(int k){
17     if(k == R){
18         //row certain
19         int result = 0;            //cur max value
20         for(int j = 0; j < C; j ++){
21             int upNum = 0;            //up numbers without fliping
22             for(int i = 0; i < R; i ++){
23                 if(a[i][j]) upNum ++;
24             }
25             result += max(upNum, R - upNum);    
26         }
27         ans = max(ans, result);
28         return;
29     }
30     //without fliping
31     dfs(k + 1);
32     //·flip
33     a[k].flip();
34     dfs(k + 1);
36     a[k].flip();
37 }
39 void solve(){
40     ans = 0;
41     dfs(0);
42     printf("%d\n", ans);
43 }
45 int main(int argc, char const *argv[]){
46 
47     while(scanf("%d %d", &R, &C)){
48         if(R == 0 && C == 0) break;
49 
50         for(int i = 0; i < R; i ++){
51             for(int j = 0; j < C; j ++){
52                 bool tmp;
53                 scanf("%d", &tmp);
54                 a[i][j] = tmp;
55             }
56         }
57         solve();
58     }
60     return 0;
61 }
Read full article from AOJ 0525 穷举 - 7hat - 博客园

Labels

LeetCode (1432) GeeksforGeeks (1122) LeetCode - Review (1067) Review (882) Algorithm (668) to-do (609) Classic Algorithm (270) Google Interview (237) Classic Interview (222) Dynamic Programming (220) DP (186) Bit Algorithms (145) POJ (141) Math (137) Tree (132) LeetCode - Phone (129) EPI (122) Cracking Coding Interview (119) DFS (115) Difficult Algorithm (115) Lintcode (115) Different Solutions (110) Smart Algorithm (104) Binary Search (96) BFS (91) HackerRank (90) Binary Tree (86) Hard (79) Two Pointers (78) Stack (76) Company-Facebook (75) BST (72) Graph Algorithm (72) Time Complexity (69) Greedy Algorithm (68) Interval (63) Company - Google (62) Geometry Algorithm (61) Interview Corner (61) LeetCode - Extended (61) Union-Find (60) Trie (58) Advanced Data Structure (56) List (56) Priority Queue (53) Codility (52) ComProGuide (50) LeetCode Hard (50) Matrix (50) Bisection (48) Segment Tree (48) Sliding Window (48) USACO (46) Space Optimization (45) Company-Airbnb (41) Greedy (41) Mathematical Algorithm (41) Tree - Post-Order (41) ACM-ICPC (40) Algorithm Interview (40) Data Structure Design (40) Graph (40) Backtracking (39) Data Structure (39) Jobdu (39) Random (39) Codeforces (38) Knapsack (38) LeetCode - DP (38) Recursive Algorithm (38) String Algorithm (38) TopCoder (38) Sort (37) Introduction to Algorithms (36) Pre-Sort (36) Beauty of Programming (35) Must Known (34) Binary Search Tree (33) Follow Up (33) prismoskills (33) Palindrome (32) Permutation (31) Array (30) Google Code Jam (30) HDU (30) Array O(N) (29) Logic Thinking (29) Monotonic Stack (29) Puzzles (29) Code - Detail (27) Company-Zenefits (27) Microsoft 100 - July (27) Queue (27) Binary Indexed Trees (26) TreeMap (26) to-do-must (26) 1point3acres (25) GeeksQuiz (25) Merge Sort (25) Reverse Thinking (25) hihocoder (25) Company - LinkedIn (24) Hash (24) High Frequency (24) Summary (24) Divide and Conquer (23) Proof (23) Game Theory (22) Topological Sort (22) Lintcode - Review (21) Tree - Modification (21) Algorithm Game (20) CareerCup (20) Company - Twitter (20) DFS + Review (20) DP - Relation (20) Brain Teaser (19) DP - Tree (19) Left and Right Array (19) O(N) (19) Sweep Line (19) UVA (19) DP - Bit Masking (18) LeetCode - Thinking (18) KMP (17) LeetCode - TODO (17) Probabilities (17) Simulation (17) String Search (17) Codercareer (16) Company-Uber (16) Iterator (16) Number (16) O(1) Space (16) Shortest Path (16) itint5 (16) DFS+Cache (15) Dijkstra (15) Euclidean GCD (15) Heap (15) LeetCode - Hard (15) Majority (15) Number Theory (15) Rolling Hash (15) Tree Traversal (15) Brute Force (14) Bucket Sort (14) DP - Knapsack (14) DP - Probability (14) Difficult (14) Fast Power Algorithm (14) Pattern (14) Prefix Sum (14) TreeSet (14) Algorithm Videos (13) Amazon Interview (13) Basic Algorithm (13) Codechef (13) Combination (13) Computational Geometry (13) DP - Digit (13) LCA (13) LeetCode - DFS (13) Linked List (13) Long Increasing Sequence(LIS) (13) Math-Divisible (13) Reservoir Sampling (13) mitbbs (13) Algorithm - How To (12) Company - Microsoft (12) DP - Interval (12) DP - Multiple Relation (12) DP - Relation Optimization (12) LeetCode - Classic (12) Level Order Traversal (12) Prime (12) Pruning (12) Reconstruct Tree (12) Thinking (12) X Sum (12) AOJ (11) Bit Mask (11) Company-Snapchat (11) DP - Space Optimization (11) Dequeue (11) Graph DFS (11) MinMax (11) Miscs (11) Princeton (11) Quick Sort (11) Stack - Tree (11) 尺取法 (11) 挑战程序设计竞赛 (11) Coin Change (10) DFS+Backtracking (10) Facebook Hacker Cup (10) Fast Slow Pointers (10) HackerRank Easy (10) Interval Tree (10) Limited Range (10) Matrix - Traverse (10) Monotone Queue (10) SPOJ (10) Starting Point (10) States (10) Stock (10) Theory (10) Tutorialhorizon (10) Kadane - Extended (9) Mathblog (9) Max-Min Flow (9) Maze (9) Median (9) O(32N) (9) Quick Select (9) Stack Overflow (9) System Design (9) Tree - Conversion (9) Use XOR (9) Book Notes (8) Company-Amazon (8) DFS+BFS (8) DP - States (8) Expression (8) Longest Common Subsequence(LCS) (8) One Pass (8) Quadtrees (8) Traversal Once (8) Trie - Suffix (8) 穷竭搜索 (8) Algorithm Problem List (7) All Sub (7) Catalan Number (7) Cycle (7) DP - Cases (7) Facebook Interview (7) Fibonacci Numbers (7) Flood fill (7) Game Nim (7) Graph BFS (7) HackerRank Difficult (7) Hackerearth (7) Inversion (7) Kadane’s Algorithm (7) Manacher (7) Morris Traversal (7) Multiple Data Structures (7) Normalized Key (7) O(XN) (7) Radix Sort (7) Recursion (7) Sampling (7) Suffix Array (7) Tech-Queries (7) Tree - Serialization (7) Tree DP (7) Trie - Bit (7) 蓝桥杯 (7) Algorithm - Brain Teaser (6) BFS - Priority Queue (6) BFS - Unusual (6) Classic Data Structure Impl (6) DP - 2D (6) DP - Monotone Queue (6) DP - Unusual (6) DP-Space Optimization (6) Dutch Flag (6) How To (6) Interviewstreet (6) Knapsack - MultiplePack (6) Local MinMax (6) MST (6) Minimum Spanning Tree (6) Number - Reach (6) Parentheses (6) Pre-Sum (6) Probability (6) Programming Pearls (6) Rabin-Karp (6) Reverse (6) Scan from right (6) Schedule (6) Stream (6) Subset Sum (6) TSP (6) Xpost (6) n00tc0d3r (6) reddit (6) AI (5) Abbreviation (5) Anagram (5) Art Of Programming-July (5) Assumption (5) Bellman Ford (5) Big Data (5) Code - Solid (5) Code Kata (5) Codility-lessons (5) Coding (5) Company - WMware (5) Convex Hull (5) Crazyforcode (5) DFS - Multiple (5) DFS+DP (5) DP - Multi-Dimension (5) DP-Multiple Relation (5) Eulerian Cycle (5) Graph - Unusual (5) Graph Cycle (5) Hash Strategy (5) Immutability (5) Java (5) LogN (5) Manhattan Distance (5) Matrix Chain Multiplication (5) N Queens (5) Pre-Sort: Index (5) Quick Partition (5) Quora (5) Randomized Algorithms (5) Resources (5) Robot (5) SPFA(Shortest Path Faster Algorithm) (5) Shuffle (5) Sieve of Eratosthenes (5) Strongly Connected Components (5) Subarray Sum (5) Sudoku (5) Suffix Tree (5) Swap (5) Threaded (5) Tree - Creation (5) Warshall Floyd (5) Word Search (5) jiuzhang (5)

Popular Posts