leetcode@ [214]Shortest Palindrome
//to be continue...
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
1 class Solution { 2 public: int* buildNext(string T){ 3 int i=1,j; 4 int *next=new int[10000000]; 5 next[0]=0; next[1]=0; 6 while(i<T.length()){ 7 j=next[i]; 8 while(j&&T[i]!=T[j]) j=next[j]; 9 next[i+1]=(T[i]==T[j])? j+1 : 0; 10 i++; 11 } 12 return next; 13 } 14 public: int KMP(int *next,string S,string T){ 15 int i=0,j=0; 16 while(i<S.length()){ 17 while(j&&S[i]!=T[j]) j=next[j]; 18 if(S[i]==T[j]) j++; 19 i++; 20 } 21 return j; 22 } 23 public: string shortestPalindrome(string s) { 24 25 string t=""; 26 for(int i=s.length()-1;i>=0;i--) t+=s[i]; 27 28 int *next=new int[s.length()]; 29 next=buildNext(s); 30 31 int add=s.length()-KMP(next,t,s); 32 33 string ans=""; 34 int i=s.length()-1; 35 while(add--){ 36 ans+=s[i]; 37 i--; 38 if(i<0) break; 39 } 40 ans+=s; 41 42 return ans; 43 } 44 };