Wednesday, May 2, 2018

LeetCode 670 - Maximum Swap


https://leetcode.com/problems/maximum-swap/description/

Given a non-negative integer, you could swap two digits at most once to get the maximum valued number. Return the maximum valued number you could get.
Example 1:
Input: 2736
Output: 7236
Explanation: Swap the number 2 and the number 7.
Example 2:
Input: 9973
Output: 9973
Explanation: No swap.
Note:
  1. The given number is in the range [0, 108]
X.
At each digit of the input number in order, if there is a larger digit that occurs later, we know that the best swap must occur with the digit we are currently considering.
Algorithm
We will compute \text{last[d] = i}, the index \text{i} of the last occurrence of digit \text{d} (if it exists).
Afterwards, when scanning the number from left to right, if there is a larger digit in the future, we will swap it with the largest such digit; if there are multiple such digits, we will swap it with the one that occurs the latest.
    public int maximumSwap(int num) {
        char[] A = Integer.toString(num).toCharArray();
        int[] last = new int[10]; //
        for (int i = 0; i < A.length; i++) {
            last[A[i] - '0'] = i;
        }

        for (int i = 0; i < A.length; i++) {
            for (int d = 9; d > A[i] - '0'; d--) {
                if (last[d] > i) {
                    char tmp = A[i];
                    A[i] = A[last[d]];
                    A[last[d]] = tmp;
                    return Integer.valueOf(new String(A));
                }
            }
        }
        return num;
    }
https://leetcode.com/problems/maximum-swap/discuss/107068/Java-simple-solution-O(n)-time


public int maximumSwap(int num) {
char[] nums = String.valueOf(num).toCharArray();

// 332()49 return
Optional<Integer> incPos = findFirstIncreasingPos(nums);
if (!incPos.isPresent()) {
// 321
return num;
}
int maxPos = findMaxPosition(nums, incPos.get());
int firstLesserPos = findFirstLesserPos(nums, incPos.get(), nums[maxPos]);
swap(nums, firstLesserPos, maxPos);
return Integer.parseInt(String.valueOf(nums));
}

// not including end
private int findFirstLesserPos(char[] nums, int end, char ch) {
for (int i = 0; i < end; i++) {
if (nums[i] < ch) { // not >
return i;
}
}

throw new RuntimeException("should never happen");
}

private void swap(char[] nums, int i, int j) {
char tmp = nums[i];
nums[i] = nums[j];
nums[j] = tmp;
}

// precondition: size >1
// 1234 return pos:1
private Optional<Integer> findFirstIncreasingPos(char[] nums) {
for (int i = 1; i < nums.length; i++) {
if (nums[i] > nums[i - 1])
return Optional.of(i);
}
return Optional.empty();
}

// precondition: must exist
// 32123()
private int findMaxPosition(char[] nums, int start) {
int maxPos = start;
for (int i = start; i < nums.length; i++) {
if (nums[i] >= nums[maxPos]) {
maxPos = i;
}
}
return maxPos;

}
https://leetcode.com/problems/maximum-swap/discuss/120360/O(n)-time-and-O(1)-space-without-using-array
I am visualizing this problem as a monotonic line from right to left with dips. So, I am traversing the number from right to left.
Objective 1- To find the number just before the dip with Max possible value. I am recording it as max and its index as maxI.
Objective 2 - To find a dip which is farthest from right. I am recording it as min and its index as minI.
If I find a dip, I am updating the max value. If there is a smaller value after the max value, then I am updating the min. Whenever there is an update in min and max, I record their Indexes and use them at the time of recreating the number.
    public int maximumSwap(int num) {
        int numC = num;
        
        int min = Integer.MAX_VALUE;
        int minI = -1;
        
        int max = Integer.MIN_VALUE;
        int maxI = -1;
        
        int pre = -1;
        int i = 0;
        
        int lmax = Integer.MIN_VALUE;
        int lmaxI = -1;
        
        //find out min and max values and their index in the num
        while(num != 0){
            int cur = num % 10;
            num = num / 10;
            
            //record increase in max value locally
            if(cur > lmax){
                lmax = cur;
                lmaxI = i +1 ;
            }
            
            //record if there is a dip
            if(cur < pre && max < lmax){
                max = lmax;
                maxI = lmaxI;
            }
            //record min value
            if(cur < max && minI < i+1){
                min = cur;
                minI = i + 1;
            }
            i++;
            pre = cur;
        }
        
        int result = 0;
        
        // re-create that number by swaping min and max
        while(i != 0){
            if(i == maxI){
                result =  result  + (min *  (int)(Math.pow(10,i-1)));
            }
            else if(i == minI){
                result =  result + (max * (int)(Math.pow(10,i-1)));
            }
            else result = result + ((numC / (int)(Math.pow(10,i -1 ))) * (int)(Math.pow(10,i-1)));
            
            numC = numC % (int)(Math.pow(10,i-1)) ;
            i--;
        }
        return result;
    }


X.
  • Time Complexity: O(N^3), where N is the total number of digits in the input number. For each pair of digits, we spend up to O(N) time to compare the final sequences.
  • Space Complexity: O(N), the information stored in \text{A}.
    public int maximumSwap(int num) {
        char[] A = Integer.toString(num).toCharArray();
        char[] ans = Arrays.copyOf(A, A.length);
        for (int i = 0; i < A.length; i++) {
            for (int j = i+1; j < A.length; j++) {
                char tmp = A[i];
                A[i] = A[j];
                A[j] = tmp;
                for (int k = 0; k < A.length; k++){
                    if (A[k] != ans[k]){
                        if (A[k] > ans[k]) {
                            ans = Arrays.copyOf(A, A.length);
                        }
                        break;
                    }
                }
                A[j] = A[i];
                A[i] = tmp;
            }
        }
        return Integer.valueOf(new String(ans));
    }



No comments:

Post a Comment

Labels

GeeksforGeeks (1109) LeetCode (1095) Review (846) Algorithm (795) to-do (634) 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) Cracking Coding Interview (110) Smart Algorithm (109) Math (108) HackerRank (89) Binary Search (83) Binary Tree (82) Graph Algorithm (76) Greedy Algorithm (73) DFS (71) Stack (65) LeetCode - Extended (62) Interview Corner (61) List (58) Advanced Data Structure (56) BFS (54) Codility (54) ComProGuide (52) Algorithm Interview (50) Geometry Algorithm (49) Trie (49) Binary Search Tree (47) USACO (46) Interval (45) LeetCode Hard (42) Mathematical Algorithm (42) ACM-ICPC (41) Data Structure (40) Knapsack (40) Space Optimization (40) Jobdu (39) Matrix (39) Recursive Algorithm (39) String Algorithm (38) Union-Find (37) Backtracking (36) Codeforces (36) Introduction to Algorithms (36) Must Known (36) Beauty of Programming (35) Sort (35) Array (33) Data Structure Design (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) Microsoft 100 - July (28) Palindrome (28) to-do-must (28) Graph (27) Random (27) Company - LinkedIn (25) GeeksQuiz (25) Logic Thinking (25) Post-Order Traverse (25) Pre-Sort (25) Time Complexity (25) hihocoder (25) Queue (24) Company-Facebook (23) High Frequency (23) TopCoder (23) Algorithm Game (22) Binary Indexed Trees (22) Bisection Method (22) Hash (22) DFS + Review (21) Lintcode - Review (21) Two Pointers (21) Brain Teaser (20) CareerCup (20) Company - Twitter (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) Long Increasing Sequence(LIS) (13) Majority (13) Reverse Thinking (13) mitbbs (13) Combination (12) Computational Geometry (12) LeetCode - Classic (12) Modify Tree (12) Reconstruct Tree (12) Reservoir Sampling (12) 尺取法 (12) AOJ (11) DFS+Backtracking (11) Fast Power Algorithm (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) Company - Microsoft (10) DFS+Cache (10) Facebook Hacker Cup (10) HackerRank Easy (10) O(1) Space (10) SPOJ (10) Theory (10) TreeMap (10) Tutorialhorizon (10) DP-Multiple Relation (9) DP-Space Optimization (9) Divide and Conquer (9) Kadane - Extended (9) Mathblog (9) Max-Min Flow (9) Prefix Sum (9) Quick Sort (9) Simulation (9) Stack Overflow (9) Stock (9) System Design (9) Use XOR (9) Book Notes (8) Bottom-Up (8) Company-Amazon (8) DFS+BFS (8) Interval Tree (8) Left and Right Array (8) Linked List (8) Longest Common Subsequence(LCS) (8) Prime (8) Suffix Tree (8) Tech-Queries (8) Traversal Once (8) 穷竭搜索 (8) Algorithm Problem List (7) Expression (7) Facebook Interview (7) Fibonacci Numbers (7) Game Nim (7) Graph BFS (7) HackerRank Difficult (7) Hackerearth (7) Inversion (7) Kadane’s Algorithm (7) Level Order Traversal (7) Math-Divisible (7) Probability DP (7) Quick Select (7) Radix Sort (7) TreeSet (7) n00tc0d3r (7) 蓝桥杯 (7) Catalan Number (6) Classic Data Structure Impl (6) DFS+DP (6) DP - Tree (6) DP-Print Solution (6) Dijkstra (6) Dutch Flag (6) How To (6) Interviewstreet (6) Knapsack - MultiplePack (6) Manacher (6) Minimum Spanning Tree (6) Morris Traversal (6) Multiple Data Structures (6) One Pass (6) Programming Pearls (6) Pruning (6) Rabin-Karp (6) Randomized Algorithms (6) Sampling (6) Schedule (6) Stream (6) Suffix Array (6) Threaded (6) Xpost (6) reddit (6) AI (5) Algorithm - Brain Teaser (5) Art Of Programming-July (5) Big Data (5) Brute Force (5) Code Kata (5) Codility-lessons (5) Coding (5) Company - WMware (5) Convex Hull (5) Crazyforcode (5) Cycle (5) DP-Include vs Exclude (5) Fast Slow Pointers (5) Find Rule (5) Graph Cycle (5) Hash Strategy (5) Immutability (5) Java (5) LeetCode - TODO (5) Matrix Chain Multiplication (5) Maze (5) Microsoft Interview (5) Pre-Sum (5) Quadtrees (5) Quick Partition (5) Quora (5) SPFA(Shortest Path Faster Algorithm) (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) Approximate Algorithm (4) Backtracking-Include vs Exclude (4) Brute Force - Enumeration (4) Chess Game (4) Consistent Hash (4) Distributed (4) Eulerian Cycle (4) Flood fill (4) Graph-Classic (4) HackerRank AI (4) Histogram (4) Kadane Max Sum (4) Knapsack - Mixed (4) Knapsack - Unbounded (4) LeetCode - Recursive (4) MST (4) MinMax (4) N Queens (4) Nerd Paradise (4) Parallel Algorithm (4) Practical Algorithm (4) Probability (4) Programcreek (4) Spell Checker (4) Stock Maximize (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) Algorithm - How To (3) Algorithm Design (3) B Tree (3) Big Data Algorithm (3) Caterpillar Method (3) Coins (3) Company - Groupon (3) Company - Indeed (3) Cumulative Sum (3) DP-Fill by Length (3) DP-Two Variables (3) Dedup (3) Dequeue (3) Dropbox (3) Easy (3) Finite Automata (3) Github (3) GoLang (3) Graph - Bipartite (3) Include vs Exclude (3) Joseph (3) Jump Game (3) K (3) Knapsack-多重背包 (3) LeetCode - Bit (3) Linked List Merge Sort (3) LogN (3) Master Theorem (3) Min Cost Flow (3) Minesweeper (3) Missing Numbers (3) NP Hard (3) O(N) Hard (3) Online Algorithm (3) Parser (3) Pascal's Triangle (3) Pattern Match (3) Project Euler (3) Rectangle (3) Scala (3) SegmentFault (3) Shuffle (3) Sieve of Eratosthenes (3) Skyline (3) Stack - Smart (3) State Machine (3) Subtree (3) Transform Tree (3) Trie + DFS (3) Two Pointers Window (3) Warshall Floyd (3) With Random Pointer (3) Word Ladder (3) bookkeeping (3) codebytes (3) Activity Selection Problem (2) Advanced Algorithm (2) AnAlgorithmADay (2) Application of Algorithm (2) Array Merge (2) BOJ (2) BT - Path Sum (2) Balanced Binary Search Tree (2) Bellman Ford (2) Binary Search - Smart (2) Binomial Coefficient (2) Bit Counting (2) Bit Mask (2) Bit-Difficult (2) Bloom Filter (2) Book Coding Interview (2) Branch and Bound Method (2) Clock (2) Codesays (2) Company - Baidu (2) Company-Snapchat (2) Complete Binary Tree (2) DFS+BFS, Flood Fill (2) DP - DFS (2) DP-3D Table (2) DP-Classical (2) DP-Output Solution (2) DP-Slide Window Gap (2) DP-i-k-j (2) DP-树形 (2) Distributed Algorithms (2) Divide and Conqure (2) Doubly Linked List (2) Edit Distance (2) Factor (2) Forward && Backward Scan (2) GoHired (2) Graham Scan (2) Graph BFS+DFS (2) Graph Coloring (2) Graph-Cut Vertices (2) Hamiltonian Cycle (2) Hard Algorithm (2) Huffman Tree (2) In-order Traverse (2) Include or Exclude Last Element (2) Information Retrieval (2) Interview - Linkedin (2) Invariant (2) Islands (2) Linked Interview (2) Linked List Sort (2) Longest SubArray (2) Lucene-Solr (2) Math-Remainder Queue (2) Matrix Power (2) Median (2) Minimum Vertex Cover (2) Negative All Values (2) Number Each Digit (2) Numerical Method (2) Object Design (2) Order Statistic Tree (2) Parent-Only Tree (2) Parentheses (2) Peak (2) Programming (2) Range Minimum Query (2) Regular Expression (2) Return Multiple Values (2) Reuse Forward Backward (2) Robot (2) Rosettacode (2) Scan from right (2) Search (2) SimHash (2) Simple Algorithm (2) Spatial Index (2) Strongly Connected Components (2) Summary (2) TV (2) Tile (2) Traversal From End (2) Tree Sum (2) Tree Traversal Return Multiple Values (2) Tree Without Tree Predefined (2) Word Break (2) Word Graph (2) Word Trie (2) Yahoo Interview (2) Young Tableau (2) 剑指Offer (2) 数位DP (2) 1-X (1) 51Nod (1) Akka (1) Algorithm - New (1) Algorithm Series (1) Algorithms Part I (1) Analysis of Algorithm (1) Array-Element Index Negative (1) Array-Rearrange (1) Augmented BST (1) Auxiliary Array (1) Auxiliary Array: Inc&Dec (1) BACK (1) BK-Tree (1) BZOJ (1) Basic (1) Bayes (1) Beauty of Math (1) Big Integer (1) Big Number (1) Binary (1) Binary Sarch Tree (1) Binary String (1) Binary Tree Variant (1) Bipartite (1) Bit-Missing Number (1) BitMap (1) BitMap index (1) BitSet (1) Bug Free Code (1) BuildIt (1) C/C++ (1) CC Interview (1) Cache (1) Calculate Height at Same Recusrion (1) Cartesian tree (1) Check Tree Property (1) Chinese (1) Circular Buffer (1) Clean Code (1) Cloest (1) Clone (1) Code Quality (1) Codesolutiony (1) Company - Alibaba (1) Company - Palantir (1) Company - WalmartLabs (1) Company-Apple (1) Company-Epic (1) Company-Salesforce (1) Company-Yelp (1) Compression Algorithm (1) Concise (1) Concurrency (1) Cont Improvement (1) Convert BST to DLL (1) Convert DLL to BST (1) Custom Sort (1) Cyclic Replacement (1) DFS-Matrix (1) DP - Probability (1) DP Fill Diagonal First (1) DP-Difficult (1) DP-End with 0 or 1 (1) DP-Fill Diagonal First (1) DP-Graph (1) DP-Left and Right Array (1) DP-MaxMin (1) DP-Memoization (1) DP-Node All Possibilities (1) DP-Optimization (1) DP-Preserve Previous Value (1) DP-Print All Solution (1) Database (1) Detect Negative Cycle (1) Diagonal (1) Directed Graph (1) Do Two Things at Same Recusrion (1) Domino (1) Dr Dobb's (1) Duplicate (1) Equal probability (1) External Sort (1) FST (1) Failure Function (1) Fraction (1) Front End Pointers (1) Funny (1) Fuzzy String Search (1) Game (1) Generating Function (1) Generation (1) Genetic algorithm (1) GeoHash (1) Geometry - Orientation (1) Google APAC (1) Graph But No Graph (1) Graph Transpose (1) Graph Traversal (1) Graph-Coloring (1) Graph-Longest Path (1) Gray Code (1) HOJ (1) Hanoi (1) How Hash (1) How to Test (1) Improve It (1) In Place (1) Inorder-Reverse Inorder Traverse Simultaneously (1) Interpolation search (1) Interview (1) Interview - Facebook (1) Isomorphic (1) JDK8 (1) K Dimensional Tree (1) Knapsack - Fractional (1) Knapsack - ZeroOnePack (1) Knight (1) Knuth Shuffle (1) Kosaraju’s algorithm (1) Kruskal (1) Kth Element (1) Least Common Ancestor (1) LeetCode - Binary Tree (1) LeetCode - Coding (1) LeetCode - Construction (1) LeetCode - Detail (1) LeetCode - Related (1) LeetCode - Thinking (1) Linked List Reverse (1) Linkedin (1) Linkedin Interview (1) Local MinMax (1) Logic Pattern (1) Longest Common Subsequence (1) Longest Common Substring (1) Longest Prefix Suffix(LPS) (1) Machine Learning (1) Maintain State (1) Manhattan Distance (1) Map && Reverse Map (1) Math - Induction (1) Math-Multiply (1) Math-Sum Of Digits (1) Matrix - O(N+M) (1) Matrix BFS (1) Matrix Graph (1) Matrix Search (1) Matrix+DP (1) Matrix-Rotate (1) Max Min So Far (1) Memory-Efficient (1) MinHash (1) MinMax Heap (1) Monotone Queue (1) Monto Carlo (1) Multi-End BFS (1) Multi-Reverse (1) Multiple DFS (1) Multiple Tasks (1) Next Element (1) Next Successor (1) Offline Algorithm (1) PAT (1) Parenthesis (1) Partition (1) Path Finding (1) Patience Sort (1) Persistent (1) Pigeon Hole Principle (1) Power Set (1) Pratical Algorithm (1) PreProcess (1) Probabilistic Data Structure (1) Python (1) Queue & Stack (1) RSA (1) Ranking (1) Rddles (1) ReHash (1) Realtime (1) Recurrence Relation (1) Recursive DFS (1) Recursive to Iterative (1) Red-Black Tree (1) Region (1) Resources (1) Reverse Inorder Traversal (1) Robin (1) Selection (1) Self Balancing BST (1) Similarity (1) Sort && Binary Search (1) Square (1) Streaming Algorithm (1) String Algorithm. Symbol Table (1) String DP (1) String Distance (1) SubMatrix (1) Subsequence (1) System of Difference Constraints(差分约束系统) (1) TSP (1) Ternary Search Tree (1) Test (1) Test Cases (1) Thread (1) TimSort (1) Top-Down (1) Tournament (1) Tournament Tree (1) Transform Tree in Place (1) Tree Diameter (1) Tree Rotate (1) Trie and Heap (1) Trie vs Hash (1) Trie vs HashMap (1) Triplet (1) Two Data Structures (1) Two Stacks (1) Two-End-BFS (1) USACO - Classical (1) USACO - Problems (1) UyHiP (1) Valid Tree (1) Vector (1) Virtual Matrix (1) Wiggle Sort (1) Wikipedia (1) ZOJ (1) ZigZag (1) baozitraining (1) codevs (1) cos126 (1) javabeat (1) jum (1) namic Programming (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)

Popular Posts