最长回文字符串 POJ3974

#include <stdio.h>
#include <iostream>
#include <string.h>
using namespace std;
const int N = 1e6 + 50;
char str[N];
char sstr[N*2];
int rad[N*2];
int manacher(char str[], int rad[])
{
    int n = strlen(str);
    int j = 0, k,ans = 0;
    for(int i = 0; i < n; i += k)
    {
        while(i-j>=0 && i+j<n && str[i-j] == str[i+j]) j++;
        rad[i] = --j;
        for(k = 1; k <= rad[i] && rad[i-k] != rad[i]-k; k++)
        {
            rad[i+k] = min(rad[i-k], rad[i]-k);
        }
        j = max(j-k, 0);
    }
    for(int i = 0; i < n; i++)
        ans = max(ans, rad[i]);
    return ans;
}
int main()
{
    int kase = 0;
    while(scanf("%s", str) != EOF)
    {
        if(strcmp(str, "END") == 0) break;
        int n = strlen(str);
        for(int i = 0; i < n; i++)
        {
            sstr[i*2] = ‘#‘;
            sstr[i*2+1] = str[i];
        }
        sstr[2*n] = ‘#‘;
        sstr[2*n+1] = ‘\0‘;
        memset(rad, 0, sizeof(rad));
        int ans=manacher(sstr, rad);
        printf("Case %d: %d\n", ++kase, ans);
    }
    return 0;
}