【HDU 3613】Best Reward

【题目链接】

           点击打开链接

【算法】

          正反两遍EXKMP，即可

【代码】

         

#include<bits/stdc++.h>
using namespace std;
#define MAXC 26
#define MAXL 500010

int T,ans,tmp,i,len;
int a[MAXC+1],Next[MAXL],extend1[MAXL],extend2[MAXL],sum[MAXL];
char s1[MAXL],s2[MAXL];

template <typename T> inline void read(T &x) {
        int f = 1; x = 0;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
        for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
        x *= f;
}
template <typename T> inline void write(T x) {
    if (x < 0) { putchar('-'); x = -x; }
    if (x > 9) write(x/10);
    putchar(x%10+'0');
}
template <typename T> inline void writeln(T x) {
    write(x);
    puts("");
}  
inline void exkmp(char *s1,char *s2,int *Next,int *Extend) {
        int i=0,j,pos;
        while (i + 1 < len && s2[i+1] == s2[i]) i++;
        Next[1] = i;
        pos = 1;
        for (i = 2; i < len; i++) {
                if (i + Next[i-pos] < pos + Next[pos]) Next[i] = Next[i-pos];
                else {
                        j = pos + Next[i-pos] - i;
                        if (j < 0) j = 0;
                        while (i + j < len && s2[j] == s2[i+j]) j++;
                        Next[i] = j;
                        pos = i;
                }
        }    
        i = 0;
        while (i < len && s1[i] == s2[i]) i++;
        Extend[0] = i;
        pos = 0;
        for (i = 1; i < len; i++) {
                if (i + Next[i-pos] < pos + Extend[pos]) Extend[i] = Next[i-pos];
                else {
                        j = pos + Extend[pos] - i;
                        if (j < 0) j = 0;
                        while (i + j < len && s1[i+j] == s2[j]) j++;
                        Extend[i] = j;
                        pos = i;
                }
        }
}

int main() {

        read(T);
        while (T--) {
                for (i = 1; i <= MAXC; i++) read(a[i]);
                scanf("%s",s1);
                len = strlen(s1);
                sum[0] = a[s1[0]-'a'+1];
                for (i = 0; i < len; i++) {
                        s2[len-i-1] = s1[i];
                        if (i > 0) sum[i] = sum[i-1] + a[s1[i]-'a'+1];
                }
                exkmp(s2,s1,Next,extend1);
                exkmp(s1,s2,Next,extend2);
                ans = 0;
                for (i = 0; i < len - 1; i++) {
                        tmp = 0;
                        if (extend1[len-i-1] == i + 1) tmp += sum[i];
                        if (extend2[i+1] == len - i - 1) tmp += sum[len-1] - sum[i];
                        ans = max(ans,tmp);
                }
                writeln(ans);
        }
        
        return 0;
    
}