hdu 3068 最长回文

参考

Grandyang
dyx404514

#include<iostream>#include<cstring>#include<cstdio>#include<algorithm>using namespace std;#define MAXN 110005char cs[MAXN],s[MAXN << 1];int p[MAXN << 1];int main(){    while(scanf("%s",cs) != EOF)    {        int len = strlen(cs);        s[0] = '$';        for(int i = 0;i <= len;i++)        {            s[i << 1 | 1] = '#';            s[(i << 1) + 2] = cs[i];        }        int idx = 0,maxn = 0,ans = 1;        for(int i = 1;i <= (len << 1);i++)        {            if(maxn > i)                p[i] = min(p[idx * 2 - i],maxn - i);            else                p[i] = 1;            for(;s[i + p[i]] == s[i - p[i]];p[i]++);            ans = max(ans,p[i] - 1);            if(i + p[i] > maxn)            {                maxn = p[i] + i;                idx = i;            }        }        printf("%d\n",ans);    }}