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 kelements 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]
对于这种题倒着处理。
主要是看两种情况,
3 1 2
要把2放后面,这1 2 3变成2 1 3,再全部倒着来一次3 1 2就OK
2 3 1这种,就直接全部倒着来就行。
class Solution { public: int arr[400]; void reverse1(int from,int to) { while(from<to){ int tmp=arr[from]; arr[from++]=arr[to]; arr[to--]=tmp; } } int Find(int num,int last){ for(int i=0;i<last;i++){ if(arr[i]==num){ return i+1; } } return 0; } void x(int len){ for(int i=0;i<len;i++){ cout<<arr[i]<<" "; } cout<<endl; } vector<int> pancakeSort(vector<int>& A) { vector<int>Ve = A; vector<int>Vee; sort(Ve.begin(),Ve.end()); int Size = A.size(); for(int i=0;i<Size;i++){ arr[i] = Ve[i]; } for(int i=0;i<Size;i++){ int address = Find(A[Size - i - 1],Size-i); if(address == 1){ //cout<<address<<" A"<<endl; reverse1(0,Size - i - 1); //x(Size); if(Size - i == 1){ continue; } Vee.push_back(Size - i); }else if(address == Size - i){ //cout<<address<<" B "<<Size - i<<endl; continue; }else{ //cout<<address<<" C"<<endl; reverse1(0,address - 1); //x(Size); if(address == 1){ continue; } Vee.push_back(address); reverse1(0,Size - i - 1); //x(Size); if(Size - i == 1){ continue; } Vee.push_back(Size - i); } } reverse(Vee.begin(),Vee.end()); return Vee; } };
原文地址:https://www.cnblogs.com/yinghualuowu/p/10230810.html
时间: 2024-10-07 18:41:57