005Longest Palindromic Substring （C）

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Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

开始竟然看成最大的逆序子串了

回文数有两种情况

（例）

1.abba

2.abgba

char* longestPalindrome(char* s) {    int i=0,k,count,countmax[2],flag=0,start,end;if(s[i]=='\0'){return NULL;}if(s[i+1]=='\0'){return s;}count=countmax[0]=0;while(s[i+1]!='\0'){if(s[i]==s[i+1]){k=0;count=0;while(i-k>=0&&s[i+1+k]!='\0'&&s[i-k]==s[i+1+k]){k++;count+=2;}}if(count>countmax[0]){countmax[0]=count;countmax[1]=i;}i++;}for(i=0;s[i+2]!='\0';i++){if(s[i]==s[i+2]){k=0;count=1;while(i-k>=0&&s[i+2+k]!='\0'&&s[i-k]==s[i+2+k]){k++;count+=2;}}if(count>countmax[0]){countmax[0]=count;countmax[1]=i+1;flag=1;}}start=end=countmax[1];for(i=0;i<countmax[0]/2;i++){if(flag==0){end++;flag=1;}else{start--;end++;}}for(i=0;start+i<=end;i++){s[i]=s[start+i];}s[i]='\0';return s;}

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