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Daily Coding Challenge #2

wingkwong profile image Wing-Kam ・2 min read

Daily Coding Challenge (88 Part Series)

1) Daily Coding Challenge #1 2) Daily Coding Challenge #2 3 ... 86 3) Daily Coding Challenge #3 4) Daily Coding Challenge #4 5) Daily Coding Challenge #5 6) Daily Coding Challenge #6 7) Daily Coding Challenge #7 8) Daily Coding Challenge #8 9) Daily Coding Challenge #9 10) Daily Coding Challenge #10 11) Daily Coding Challenge #11 12) Daily Coding Challenge #12 13) Daily Coding Challenge #13 14) Daily Coding Challenge #14 15) Daily Coding Challenge #15 16) Daily Coding Challenge #16 17) Daily Coding Challenge #17 18) Daily Coding Challenge #18 19) Daily Coding Challenge #19 20) Daily Coding Challenge #20 21) Daily Coding Challenge #21 22) Daily Coding Challenge #22 23) Daily Coding Challenge #23 24) Daily Coding Challenge #24 25) Daily Coding Challenge #25 26) Daily Coding Challenge #26 27) Daily Coding Challenge #27 28) Daily Coding Challenge #28 29) Daily Coding Challenge #29 30) Daily Coding Challenge #30 31) Daily Coding Challenge #31 32) Daily Coding Challenge #32 33) Daily Coding Challenge #33 34) Daily Coding Challenge #34 35) Daily Coding Challenge #35 36) Daily Coding Challenge #36 37) Daily Coding Challenge #37 38) Daily Coding Challenge #38 39) Daily Coding Challenge #39 40) Daily Coding Challenge #40 41) Daily Coding Challenge #41 42) Daily Coding Challenge #42 43) Daily Coding Challenge #43 44) Daily Coding Challenge #44 45) Daily Coding Challenge #45 46) Daily Coding Challenge #46 47) Daily Coding Challenge #47 48) Daily Coding Challenge #48 49) Daily Coding Challenge #49 50) Daily Coding Challenge #50 51) Daily Coding Challenge #51 52) Daily Coding Challenge #52 53) Daily Coding Challenge #53 54) Daily Coding Challenge #54 55) Daily Coding Challenge #55 56) Daily Coding Challenge #56 57) Daily Coding Challenge #57 58) Daily Coding Challenge #58 59) Daily Coding Challenge #59 60) Daily Coding Challenge #60 61) Daily Coding Challenge #61 62) Daily Coding Challenge #62 63) Daily Coding Challenge #63 64) Daily Coding Challenge #64 65) Daily Coding Challenge #65 66) Daily Coding Challenge #66 67) Daily Coding Challenge #67 68) Daily Coding Challenge #68 69) Daily Coding Challenge #69 70) Daily Coding Challenge #70 71) Daily Coding Challenge #71 72) Daily Coding Challenge #72 73) Daily Coding Challenge #73 74) Daily Coding Challenge #74 75) Daily Coding Challenge #75 76) Daily Coding Challenge #76 77) Daily Coding Challenge #77 78) Daily Coding Challenge #78 79) Daily Coding Challenge #79 80) Daily Coding Challenge #80 81) Daily Coding Challenge #81 82) Daily Coding Challenge #82 83) Daily Coding Challenge #83 84) Daily Coding Challenge #84 85) Daily Coding Challenge #85 86) Daily Coding Challenge #86 87) Daily Coding Challenge #87 88) Daily Coding Challenge #88

About

This is a series of Daily Coding Challenge. Each day I show a few solutions written in C++. The questions are from coding practice/contest sites such as HackerRank, LeetCode, Codeforces, Atcoder and etc.


/*
Leetcode - Pancake Sorting

Given an array A, we can perform a pancake flip: We choose some positive integer k <= A.length, then reverse the order of the first k elements of A.  We want to perform zero or more pancake flips (doing them one after another in succession) to sort the array A.

Return the k-values corresponding to a sequence of pancake flips that sort A.  Any valid answer that sorts the array within 10 * A.length flips will be judged as correct.

Example 1:

Input: [3,2,4,1]
Output: [4,2,4,3]
Explanation: 
We perform 4 pancake flips, with k values 4, 2, 4, and 3.
Starting state: A = [3, 2, 4, 1]
After 1st flip (k=4): A = [1, 4, 2, 3]
After 2nd flip (k=2): A = [4, 1, 2, 3]
After 3rd flip (k=4): A = [3, 2, 1, 4]
After 4th flip (k=3): A = [1, 2, 3, 4], which is sorted. 
Example 2:

Input: [1,2,3]
Output: []
Explanation: The input is already sorted, so there is no need to flip anything.
Note that other answers, such as [3, 3], would also be accepted.


Note:

1 <= A.length <= 100
A[i] is a permutation of [1, 2, ..., A.length]
*/

class Solution {
public:
    vector<int> pancakeSort(vector<int>& A) {
        int sz=(int)A.size();
        vector<int> ans;
        for(int i=0;i<sz;i++){
            auto mp=max_element(A.begin(),A.end()-i);
            ans.push_back(mp-A.begin()+1);
            ans.push_back(sz-i);
            reverse(A.begin(),mp+1);
            reverse(A.begin(),A.end()-i);
        }
        return ans;
    }
};

// Test case: 3,2,4,1
// -------------
// i:0;n=4;
// 3 2 [4] 1  // find the max number A[mp] from 0..n-1-i / A[2]=4 is the max from 0..3
// 4 2 3 1    // reverse 0..mp+1 numbers. [ 3 2 4 ] -> [ 4 2 3 ]. 1 keeps at the same place
// 1 3 2 4    // reverse 0..n-1-i. [ 4 2 3 1 ] to [ 1 3 2 4 ]
// --------------
// i:1;n=4;
// 1 3 2 4   // now the largest value is located at the end, 4 is fixed here and find the max number from 0..n-1-i
// 3 1 2 4   // the max number is 3, reverse the first two numbers [ 1 3 ] -> [ 3 1 ] while [ 2 4 ] keeps at the same place
// 2 1 3 4   // reverse 0..n-1-i [ 3 1 2 4 ] -> [ 2 1 3 4 ]
// --------------
// i:2;n=4;
// 2 1 3 4   // similarly, perform the same action
// 2 1 3 4   // the max number is located index 0, no action is made here 
// 1 2 3 4   // reverse 0..n-1-i [ 2 1 3 4 ] -> [ 1 2 3 4 ]
// --------------
// i:3;n=4;
// 1 2 3 4   // already sorted. no action is performed
// 1 2 3 4 
// 1 2 3 4 
// --------------

The source code is available in corresponding repo below. Star and watch for timely updates!

GitHub logo wingkwong / leetcode

πŸ† A Collection of my LeetCode Solutions with Explanations πŸ†

GitHub logo wingkwong / hackerrank

πŸ† A Collection of my HackerRank Solutions with Explanations πŸ†

GitHub logo wingkwong / codeforces

πŸ† A Collection of my Codeforces Solutions with Explanations πŸ†

GitHub logo wingkwong / atcoder

πŸ† A Collection of my AtCoder Solutions with Explanations πŸ†

Daily Coding Challenge (88 Part Series)

1) Daily Coding Challenge #1 2) Daily Coding Challenge #2 3 ... 86 3) Daily Coding Challenge #3 4) Daily Coding Challenge #4 5) Daily Coding Challenge #5 6) Daily Coding Challenge #6 7) Daily Coding Challenge #7 8) Daily Coding Challenge #8 9) Daily Coding Challenge #9 10) Daily Coding Challenge #10 11) Daily Coding Challenge #11 12) Daily Coding Challenge #12 13) Daily Coding Challenge #13 14) Daily Coding Challenge #14 15) Daily Coding Challenge #15 16) Daily Coding Challenge #16 17) Daily Coding Challenge #17 18) Daily Coding Challenge #18 19) Daily Coding Challenge #19 20) Daily Coding Challenge #20 21) Daily Coding Challenge #21 22) Daily Coding Challenge #22 23) Daily Coding Challenge #23 24) Daily Coding Challenge #24 25) Daily Coding Challenge #25 26) Daily Coding Challenge #26 27) Daily Coding Challenge #27 28) Daily Coding Challenge #28 29) Daily Coding Challenge #29 30) Daily Coding Challenge #30 31) Daily Coding Challenge #31 32) Daily Coding Challenge #32 33) Daily Coding Challenge #33 34) Daily Coding Challenge #34 35) Daily Coding Challenge #35 36) Daily Coding Challenge #36 37) Daily Coding Challenge #37 38) Daily Coding Challenge #38 39) Daily Coding Challenge #39 40) Daily Coding Challenge #40 41) Daily Coding Challenge #41 42) Daily Coding Challenge #42 43) Daily Coding Challenge #43 44) Daily Coding Challenge #44 45) Daily Coding Challenge #45 46) Daily Coding Challenge #46 47) Daily Coding Challenge #47 48) Daily Coding Challenge #48 49) Daily Coding Challenge #49 50) Daily Coding Challenge #50 51) Daily Coding Challenge #51 52) Daily Coding Challenge #52 53) Daily Coding Challenge #53 54) Daily Coding Challenge #54 55) Daily Coding Challenge #55 56) Daily Coding Challenge #56 57) Daily Coding Challenge #57 58) Daily Coding Challenge #58 59) Daily Coding Challenge #59 60) Daily Coding Challenge #60 61) Daily Coding Challenge #61 62) Daily Coding Challenge #62 63) Daily Coding Challenge #63 64) Daily Coding Challenge #64 65) Daily Coding Challenge #65 66) Daily Coding Challenge #66 67) Daily Coding Challenge #67 68) Daily Coding Challenge #68 69) Daily Coding Challenge #69 70) Daily Coding Challenge #70 71) Daily Coding Challenge #71 72) Daily Coding Challenge #72 73) Daily Coding Challenge #73 74) Daily Coding Challenge #74 75) Daily Coding Challenge #75 76) Daily Coding Challenge #76 77) Daily Coding Challenge #77 78) Daily Coding Challenge #78 79) Daily Coding Challenge #79 80) Daily Coding Challenge #80 81) Daily Coding Challenge #81 82) Daily Coding Challenge #82 83) Daily Coding Challenge #83 84) Daily Coding Challenge #84 85) Daily Coding Challenge #85 86) Daily Coding Challenge #86 87) Daily Coding Challenge #87 88) Daily Coding Challenge #88

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Wing-Kam

@wingkwong

Consultant by day. Developer by night. AWS certified. Exploring #CloudNative currently.

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