A、B两个整数集合的交集 - BrilliantEagle的专栏 - 博客频道 - CSDN.NET


A、B两个整数集合的交集 - BrilliantEagle的专栏 - 博客频道 - CSDN.NET
用数组来模拟(本质上说集合中是没有重复元素的,这里用数组来模拟可以用重复元素),AB数组长度分别为mn。总的来说,分为以下几种方案。

方案1:两重循环判断(复杂度 Om*n))

暴力方法,并且不容易去除重复元素

方案2:Hash Table方法(复杂度 Om+n))

   A写入Hash Table,让后BHash Tabe中写入过程中判断重复即可。如果没有重复元素,唯一缺点是内存占用量大,可以使用《编程珠玑》中的BitMap方法节省内存。另外Hash过程中可能会有比较多的冲突。
另外,本方法不具有普遍性。

方案3:排序后对A中每个元素在B中进行二分查找(复杂度 O(nlogn+mlogm)

    这里m<=n。否则排序后对B中每个元素在A中进行二分查找(复杂度 On*lgm

注意,排序的复杂度是O(nlogn+mlogm),查找的复杂度是On*lgm)。

方案4:排序后应用归并排序的思想进行判断(复杂度 O(nlogn+mlogm)

   指针ij分别指向AB的开头,如果对应元素相等即为交集,否则谁小谁的指针加1往后移动。

http://www.cnblogs.com/bestdavid/p/examinationtencent.html
思路3:集合压缩
  对于一个集合来说,我们很容易就可以得到集合的最大值和最小值,假设集合A的最大值和最小值分别为MaxInA,MinInA;假设集合B的最大值和最小值分别为MaxInB,MinInB;那么集合A的所有元素一定在闭区间【MinInA, MaxInA】里面,集合B的所有元素一定在闭区间【MinInB, MaxInB】里面,从这两个集合里面我们可以作如下判断:(集合A和集合B都在链表中!此算法使用链表结构,操作起来比数组更方便)

  1. 若MinInA == MinInB或者MaxInA == MaxInB,那么MinInA 或者MaxInA (相等的那个数)就一定在交集里面,存入交集(可以用数组存),删除链表中相应的结点;若不想等则跳到第3步;

  2. 重新找到集合A和B中的最大值和最小值MinInA 、MaxInA 、MinInB、MaxInB;跳回第1步;

  3. 更新区间(交集的区间),区间的更新如下:区间下界为Lower = max(MinInA, MinInB),上届为Upper = min(MaxInA , MaxInB),那么剩下的交集一定在闭区间【Lower ,Upper】里面,按照这个区间来剔除掉集合A和集合B中不符合条件的元素,剔除结束后,若其中一个集合为空,跳到第4步,否则返回第2步;

  4. 程序结束,退出!

  这种适用于集合里面数值比较散乱,最大值最小值差值比较大的情况!算法的思想在于不断减小搜索的范围,时间的消耗主要在查找集合的最大值和最小值上,我们来看一个例子,集合A= {1, 3, 10, 100, 123, 0, 6} ,B = {3, 2, 10, 23, -1},

  集合A的闭区间【0, 123】,集合B的区间【-1,23】,交集的闭区间就为【0,23】,按照这个区间,剔除集合A中的{ 100, 123},剔除集合B的{-1},集合A={1, 3, 10, 0, 6}集合B={3, 2, 10, 23},没有相等的,继续缩小范围,为【2,10】,这时MaxInA == MaxInB,满足条件,把10存入交集数组中,剔除两个集合的结点;集合变为A= {3,6}集合B={3},满足MinInA == MinInB或者MaxInA == MaxInB,把3存入交集数组中,集合B为空,结束!如图:


  对于第三个方法,我只是把算法的思想做了一下总结,并没有编写代码运行调试并与其他算法做比较!比较过的朋友,欢迎告知三种算法的优劣性!
Read full article from A、B两个整数集合的交集 - BrilliantEagle的专栏 - 博客频道 - CSDN.NET

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