## Sunday, May 15, 2016

### Cavity Map

https://github.com/xieqilu/Qilu-leetcode/blob/master/B223.CavityMap.cs
You are given a square map of size n×n. Each cell of the map has a value denoting its depth. We will call a cell of the map
a cavity if and only if this cell is not on the border of the map and each cell adjacent to it has strictly smaller depth.
Two cells are adjacent if they have a common side.
You need to find all the cavities on the map and depict them with the uppercase character X.

Input Format
The first line contains an integer, n, denoting the size of the map. Each of the following n lines contains n positive digits without spaces.
Each digit (1-9) denotes the depth of the appropriate area.
Constraints
1≤n≤100
Output Format
Output n lines, denoting the resulting map. Each cavity should be replaced with character X.
Sample Input
4
1112
1912
1892
1234
Sample Output
1112
1X12
18X2
1234

This is a very simple problem, but there are some points to be noticed. The method is just traverse the whole map, if current cell is a border cell, output its value. Then compare current cell with all four adjacent cells, if the value of current cell is larger than all four adjacent cells, output "X". Otherwise output its value.

Note:
1, When parse the input and build a 2D int array (matrix), the line of input doesn't contain any space. So converse the line to
a char array using string.ToCharArray(), then map[i,j] = line[j]-'0'. Don't try to use int.Parse to convert a string array to int.
Think outside of the box.
2, Don't try to modify the value of the matrix then output the whole matrix. This will require an extra traverse which is not efficient. Besides, we cannot change the value of an integer cell to "X", it's better to output the result when traversing the matrix. Then we only need to traverse for once.
public static void FindCavity(int[,] map, int size){
for(int i=0;i<size;i++){
for(int j=0;j<size;j++){
if(i==0 || j==0 || i==size-1 || j==size-1)
Console.Write(map[i,j]);
else if(map[i,j]>map[i-1,j]&&map[i,j]>map[i+1,j]&&map[i,j]>map[i,j+1]&&map[i,j]>map[i,j-1])
Console.Write("X");
else
Console.Write(map[i,j]);
}
Console.WriteLine(); //start a new line
}
}

static void Main(String[] args) {
/* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
int size = int.Parse(Console.ReadLine());
int[,] map = new int[size,size];
for(int i=0;i<size;i++){
char[] line = Console.ReadLine().ToCharArray();
for(int j=0;j<size;j++)
map[i,j] = line[j]-'0';
}
FindCavity(map,size);
}

## Labels

GeeksforGeeks (1109) LeetCode (1095) Review (846) Algorithm (795) to-do (633) LeetCode - Review (574) Classic Algorithm (324) Dynamic Programming (294) Classic Interview (288) Google Interview (242) Tree (145) POJ (139) Difficult Algorithm (132) LeetCode - Phone (127) EPI (125) Bit Algorithms (120) Different Solutions (120) Lintcode (113) Smart Algorithm (109) Math (108) HackerRank (89) Binary Search (83) Binary Tree (82) Graph Algorithm (76) Greedy Algorithm (73) DFS (71) Stack (65) Interview Corner (61) List (58) BFS (54) Codility (54) ComProGuide (52) Trie (49) USACO (46) Interval (45) LeetCode Hard (42) ACM-ICPC (41) Data Structure (40) Knapsack (40) Jobdu (39) Matrix (39) String Algorithm (38) Union-Find (37) Backtracking (36) Codeforces (36) Must Known (36) Sort (35) Array (33) Segment Tree (33) Sliding Window (33) prismoskills (33) HDU (31) Priority Queue (31) Google Code Jam (30) Permutation (30) Puzzles (30) Array O(N) (29) Company-Airbnb (29) Company-Zenefits (28) Palindrome (28) to-do-must (28) Graph (27) Random (27) GeeksQuiz (25) Logic Thinking (25) Pre-Sort (25) Time Complexity (25) hihocoder (25) Queue (24) Company-Facebook (23) High Frequency (23) TopCoder (23) Algorithm Game (22) Bisection Method (22) Hash (22) DFS + Review (21) Two Pointers (21) Brain Teaser (20) CareerCup (20) LeetCode - DP (20) Merge Sort (20) O(N) (20) Follow Up (19) UVA (19) Ordered Stack (18) Probabilities (18) Company-Uber (17) Game Theory (17) Topological Sort (17) Codercareer (16) Heap (16) Shortest Path (16) String Search (16) Tree Traversal (16) itint5 (16) Difficult (15) Iterator (15) BST (14) KMP (14) LeetCode - DFS (14) Number (14) Number Theory (14) Amazon Interview (13) Basic Algorithm (13) Codechef (13) Euclidean GCD (13) Majority (13) Reverse Thinking (13) mitbbs (13) Combination (12) Modify Tree (12) Reconstruct Tree (12) 尺取法 (12) AOJ (11) DFS+Backtracking (11) Graph DFS (11) LCA (11) Miscs (11) Princeton (11) Proof (11) Rolling Hash (11) Tree DP (11) X Sum (11) 挑战程序设计竞赛 (11) Bisection (10) Bucket Sort (10) Coin Change (10) DFS+Cache (10) HackerRank Easy (10) O(1) Space (10) SPOJ (10) Theory (10) TreeMap (10) Tutorialhorizon (10) Mathblog (9) Max-Min Flow (9) Prefix Sum (9) Quick Sort (9) Simulation (9) Stock (9) Use XOR (9) Book Notes (8) Bottom-Up (8) DFS+BFS (8) Linked List (8) Prime (8) Suffix Tree (8) Tech-Queries (8) 穷竭搜索 (8) Expression (7) Game Nim (7) Graph BFS (7) Hackerearth (7) Inversion (7) Quick Select (7) Radix Sort (7) TreeSet (7) n00tc0d3r (7) 蓝桥杯 (7) DFS+DP (6) DP - Tree (6) Dijkstra (6) Dutch Flag (6) How To (6) Manacher (6) One Pass (6) Pruning (6) Rabin-Karp (6) Sampling (6) Schedule (6) Stream (6) Suffix Array (6) Threaded (6) Xpost (6) reddit (6) AI (5) Big Data (5) Brute Force (5) Code Kata (5) Coding (5) Convex Hull (5) Crazyforcode (5) Cycle (5) Find Rule (5) Graph Cycle (5) Immutability (5) Java (5) Maze (5) Pre-Sum (5) Quadtrees (5) Quora (5) Subarray Sum (5) Sudoku (5) Sweep Line (5) Word Search (5) jiuzhang (5) 单调栈 (5) 树形DP (5) 1point3acres (4) Abbreviation (4) Anagram (4) Anagrams (4) Chess Game (4) Distributed (4) Flood fill (4) Histogram (4) MST (4) MinMax (4) N Queens (4) Probability (4) Programcreek (4) Subset Sum (4) Subsets (4) Symbol Table (4) Triangle (4) Water Jug (4) algnotes (4) fgdsb (4) to-do-2 (4) 最大化最小值 (4) A Star (3) B Tree (3) Coins (3) Dedup (3) Dequeue (3) Dropbox (3) Easy (3) Github (3) GoLang (3) Joseph (3) Jump Game (3) K (3) LogN (3) Minesweeper (3) NP Hard (3) O(N) Hard (3) Parser (3) Rectangle (3) Scala (3) SegmentFault (3) Shuffle (3) Skyline (3) Subtree (3) Trie + DFS (3) Word Ladder (3) bookkeeping (3) codebytes (3) Array Merge (2) BOJ (2) Bellman Ford (2) Bit Counting (2) Bit Mask (2) Bloom Filter (2) Clock (2) Codesays (2) DP - DFS (2) DP-3D Table (2) DP-Classical (2) DP-i-k-j (2) DP-树形 (2) Factor (2) GoHired (2) Graham Scan (2) Huffman Tree (2) Invariant (2) Islands (2) Lucene-Solr (2) Matrix Power (2) Median (2) Parentheses (2) Peak (2) Programming (2) Robot (2) Rosettacode (2) Search (2) SimHash (2) Summary (2) TV (2) Tile (2) Tree Sum (2) Word Break (2) Word Graph (2) Word Trie (2) 剑指Offer (2) 数位DP (2) 1-X (1) 51Nod (1) Akka (1) BACK (1) BK-Tree (1) BZOJ (1) Basic (1) Bayes (1) Big Integer (1) Big Number (1) Binary (1) Bipartite (1) BitMap (1) BitMap index (1) BitSet (1) BuildIt (1) C/C++ (1) CC Interview (1) Cache (1) Chinese (1) Clean Code (1) Cloest (1) Clone (1) Code Quality (1) Company-Epic (1) Company-Yelp (1) Concise (1) Concurrency (1) Custom Sort (1) DFS-Matrix (1) DP-Difficult (1) DP-Graph (1) DP-MaxMin (1) Database (1) Diagonal (1) Domino (1) Dr Dobb's (1) Duplicate (1) FST (1) Fraction (1) Funny (1) Game (1) Generation (1) GeoHash (1) Google APAC (1) Gray Code (1) HOJ (1) Hanoi (1) How Hash (1) How to Test (1) Improve It (1) In Place (1) Interview (1) Isomorphic (1) JDK8 (1) Knight (1) Kruskal (1) Kth Element (1) Linkedin (1) Local MinMax (1) Matrix BFS (1) Matrix Graph (1) Matrix+DP (1) MinHash (1) MinMax Heap (1) Monto Carlo (1) Multiple DFS (1) Next Element (1) PAT (1) Parenthesis (1) Partition (1) Path Finding (1) Persistent (1) Power Set (1) PreProcess (1) Python (1) RSA (1) Ranking (1) Rddles (1) ReHash (1) Realtime (1) Region (1) Resources (1) Robin (1) Selection (1) Similarity (1) Square (1) String DP (1) SubMatrix (1) Subsequence (1) TSP (1) Test (1) Test Cases (1) Thread (1) TimSort (1) Top-Down (1) Tournament (1) Tree Rotate (1) Trie vs Hash (1) Triplet (1) Two Stacks (1) Two-End-BFS (1) UyHiP (1) Valid Tree (1) Vector (1) Wiggle Sort (1) Wikipedia (1) ZOJ (1) ZigZag (1) codevs (1) cos126 (1) javabeat (1) jum (1) sqrt(N) (1) 两次dijkstra (1) 九度 (1) 二进制枚举 (1) 夹逼法 (1) 归一化 (1) 折半枚举 (1) 枚举 (1) 状态压缩DP (1) 男人八题 (1) 英雄会 (1) 逆向思维 (1)