【BZOJ 3790】 神奇项链

【题目链接】

https://www.lydsy.com/JudgeOnline/problem.php?id=3790

【算法】

manacher + 贪心

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN 500010

char s[MAXN];

struct info
{
        int l,r;
};
inline bool cmp(info a,info b)
{
        return a.l != b.l ? a.l < b.l : a.r > b.r;
}
inline void Manacher()
{
        int i,len,pos = ,mx = ,n = ,ans,r;
        static int p[MAXN<<];
        static char tmp[MAXN<<];
        static info a[MAXN<<];
        len = strlen(s+);
        for (i = ; i <= len; i++)
        {
                tmp[*i-] = '#';
                tmp[*i] = s[i];
        }
        tmp[len =  * len + ] = '#';
        for (i = ; i <= len; i++)
        {
                if (mx > i) p[i] = min(p[*pos-i],mx-i);
                else p[i] = ;
                while (i - p[i] >=  && i + p[i] <= len && tmp[i-p[i]] == tmp[i+p[i]]) p[i]++;
                if (i + p[i] -  > mx)
                {
                        mx = i + p[i] - ;
                        pos = i;
                }
        }
        for (i = ; i <= len; i++) a[++n] = (info){i-p[i]+,i+p[i]-};
        sort(a+,a+n+,cmp);
        r = a[].r; ans = ; pos = ;
        while (r < len)
        {
                mx = r;
                while (pos <= n && a[pos].l <= r + )
                {
                        mx = max(mx,a[pos].r);
                        pos++;
                }
                ans++;
                r = mx;
        }
        printf("%d\n",ans-);
}

int main()
{

        while (scanf("%s",s+) != EOF) Manacher();

        return ;

}