POJ 2386 Lake Counting search question, poj2386

POJ 2386 Lake Counting search question, poj2386

Simple Deep Search is enough. When someone says what to use and query the set, it is a small use of big algorithms.

Because it can be searched in depth without backtracking, the efficiency is O (N * M.

The trick is to add a sign P. Every time a pond is searched, there is a W letter, so it is considered that a pond is searched, and the P value is true.

Do not repeat the searched pond. Therefore, every time you walk through the pond, you can change it to another letter, such as '@' or.

Then, search in 8 directions.

#include <stdio.h>#include <vector>#include <string.h>#include <algorithm>#include <iostream>#include <string>#include <limits.h>#include <stack>#include <queue>#include <set>#include <map>using namespace std;const int MAX_N = 101;char pond[MAX_N][MAX_N];const char VIS = '@';int N, M;bool P;inline bool isLegal(int r, int c){return 0<=r && 0<=c && r<N && c<M && pond[r][c] == 'W';}void getPond(int r, int c){if (!isLegal(r, c)) return ;P = true;pond[r][c] = VIS;getPond(r+1, c);getPond(r-1, c);getPond(r, c+1);getPond(r, c-1);getPond(r+1, c+1);getPond(r+1, c-1);getPond(r-1, c+1);getPond(r-1, c-1);//eight direction search}int main(){while (~scanf("%d %d", &N, &M)){getchar();for (int i = 0; i < N; i++){gets(pond[i]);}int ans = 0;for (int i = 0; i < N; i++){for (int j = 0; j < M; j++){P = false;getPond(i, j);ans += P;}}printf("%d\n", ans);}return 0;}

ACM solution report

Category of a poj question
Mainstream algorithms:
1. Search // trace back
2. DP (Dynamic Planning)
3. Greedy
4. Graph Theory // Dijkstra, Minimum Spanning Tree, and network stream
5. Number Theory // solves the modulus linear equation
6. Calculate the area and perimeter of the joint of the geometric/Convex Shell with the same placement of the rectangle
7. Composite math // Polya Theorem
8. Simulation
9. Data Structure // check the collection and heap
10. Game Theory
1. Sorting
1423,169 4, 1723,172 7, 1763,178 8, 1828,183 8, 1840,220 1, 2376,
2377,238 0, 1318,187 1971,197, 1990,200 4, 2002,209 1, 2379 2,
1002 (character processing is required, and sorting can be done in a fast way) 1007 (stable sorting) 2159 (difficult to understand)
2231 2371 (simple sorting) 2388 (sequence statistics algorithm) 2418 (Binary sorting tree)
2. Search, backtracking, and traversal
2329
Simple: 1128,116 6, 1176,123 1, 1256,127 0, 1321,154 3, 1606,166 4,
1731,174 2, 1745,184, 1950,203, 2157,218 8, 2183,238 2, 2386,242 1, 6
Not easy: 1024,105 4, 1117,116 7, 1708,174 6, 1775,187 8, 1903,196 6, 2046,
2197,234 9
Recommended: 1011,119 0, 1191,141 6, 1579,163 2, 1639,165 9, 1680,168 3, 1691,
1709,171 4, 1753,1771, 1826,185 5, 1856,189 0, 1924,193 5, 1948,197 9, 1980,217 2331,233 1979, 1980 9, (similar to the maze), (higher requirements for pruning)
3. Calendar
1008 2080 (Be careful with such questions)
4. Enumeration
1387,141, 2245,232, 2363,238 1, 1650 6, (higher pruning requirements), (decimal precision problem)
5. Typical data structure Algorithms
Easy: 1182,165 6, 2021,202 3, 2051,215 3, 2227,223 6, 2247,235 2,
2395
Not easy: 1145,117 7, 1195,122 7, 1661,183 4
Recommended: 1330,133 8, 1451,147 0, 1634,168 9, 1693,170 3, 1724,198 8, 2004,
2010,211 9, 2274
1125 (fresh algorithm), 2421 (Minimum Spanning Tree of the graph)
6. Dynamic Planning
1037 A decorative fence,
1050 To the Max,
1088 skiing,
1125 Stockbroker Grapevine,
1141 Brackets Sequence,
1159 Palindrom ...... remaining full text>

Categories of topics on acm

Let me have a look at this information.
Peking University ACM (PKU JudgeOnline) subject category
1. Search // trace back
2. DP (Dynamic Planning)
3. Greedy
4. Graph Theory // Dijkstra, Minimum Spanning Tree, and network stream
5. Number Theory // solves the modulus linear equation
6. Calculate the area and perimeter of the joint of the geometric/Convex Shell with the same placement of the rectangle
7. Composite math // Polya Theorem
8. Simulation
9. Data Structure // check the collection and heap
10. Game Theory
1. Sorting
1423,169 4, 1723,172 7, 1763,178 8, 1828,183 8, 1840,220 1, 2376,237 7, 2380,131 8, 1877,192, 1971,

1974,199 0, 2001,200 2, 2092,237 9,
1002 (character processing is required, and sorting can be done in a fast way) 1007 (stable sorting) 2159 (difficult to understand) 2231 2371 (simple sorting)

2388 (sequential statistics algorithm) 2418 (Binary sorting tree)
2. Search, backtracking, and traversal
1022 1111d 1118 1129 1190 1562 1564 1573 1655 2184 2225 2243 2312 2362 2378 2386

1010,1011, 1018,1020, 1054,1062, 1256,1321, 1363,1501, 1650,1659, 1664,1753, 2078
, 2083,2303, 2310,2329
Simple: 1128,116 6, 1176,123 1, 1256,127 0, 1321,154 3, 1606,166 4, 1731,174 2, 1745,184 7, 1915,195 0,

2038,215 7, 2182,218 3, 2381,238 6, 2426,
Not easy: 1024,105 4, 1117,116 7, 1708,174 6, 1775,187 8, 1903,196 6, 2046,219 7, 2349,
Recommended: 1011,119 0, 1191,141 6, 1579,163 2, 1639,165 9, 1680,168 3, 1691,170 9, 1714,175 3, 1771,182 6,

1855,185 6, 1890,192 4, 1935,194 8, 1979,198 0, 2170,228 8, 2331,233 9, 2340,1979 (similar to the maze) 1980 (for pruning

High requirements)
3. Calendar
1008 2080 (Be careful with such questions)
4. Enumeration
1387,141, 2245,232, 2363,238 1, 1650 6, (high requirements for pruning), (decimal precision Problem

)
5. Typical data structure Algorithms
Easy: 1182,165 6, 2021,202 3, 2051,215 3, 2227,223 6, 2247,235 2, 2395,
Not easy: 1145,117 7, 1195,122 7, 1661,183 4,
Recommendation: 1330,133 8, 1451,147 0, 1634,168 9, 1693,170 3, 1724,198 8, 2004,201 0, 2119,227 4, 1125

Method), 2421 (Minimum Spanning Tree of the graph)
6. Dynamic Planning
... The remaining full text>