HDU - 4552 怪盗基德的挑战书 (后缀数组)

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 aaa
abab 

 6
6 

题意：求前缀在串出现的次数。
思路：利用后缀数组求，求每个后缀与原串的匹配长度，因为和原串匹配，所以和原串的最长公共前缀都可以表示为前缀。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
typedef long long ll;
using namespace std;
const int maxn = 100010;

int sa[maxn]; 
int t1[maxn], t2[maxn], c[maxn];
int rank[maxn], height[maxn];

void build_sa(int s[], int n, int m) {
    int i, j, p, *x = t1, *y = t2;
    for (i = 0; i < m; i++) c[i] = 0;
    for (i = 0; i < n; i++) c[x[i] = s[i]]++;
    for (i = 1; i < m; i++) c[i] += c[i-1];
    for (i = n-1; i >= 0; i--) sa[--c[x[i]]] = i;

    for (j = 1; j <= n; j <<= 1) {
        p = 0;
        for (i = n-j; i < n; i++) y[p++] = i;
        for (i = 0; i < n; i++) 
            if (sa[i] >= j) 
                y[p++] = sa[i] - j;
        for (i = 0; i < m; i++) c[i] = 0;
        for (i = 0; i < n; i++) c[x[y[i]]]++;
        for (i = 1; i < m; i++) c[i] += c[i-1];
        for (i = n-1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i];

        swap(x, y);
        p = 1, x[sa[0]] = 0;
        for (i = 1; i < n; i++) 
            x[sa[i]] = y[sa[i-1]] == y[sa[i]] && y[sa[i-1]+j] == y[sa[i]+j] ? p-1 : p++;

        if (p >= n) break;
        m = p;
    }
}

void getHeight(int s[],int n) {
    int i, j, k = 0;
    for (i = 0; i <= n; i++)
        rank[sa[i]] = i;

    for (i = 0; i < n; i++) {
        if (k) k--;
        j = sa[rank[i]-1];
        while (s[i+k] == s[j+k]) k++;
        height[rank[i]] = k;
    }
}

char str[maxn];
int r[maxn];

int main() {
    while (scanf("%s", str) != EOF) {
        int n = strlen(str);
        for (int i = 0; i <= n; i++)
            r[i] = str[i];

        build_sa(r, n+1, 128);
        getHeight(r, n);

        int ans = n;
        int mid = rank[0];
        int tmp = n;
        while (mid < n) {
            tmp = min(tmp, height[mid+1]);
            mid++;
            ans += tmp;
        }
        mid = rank[0];
        tmp = n;
        while (mid > 1) {
            tmp = min(tmp, height[mid]);
            mid--;
            ans += tmp;
        }

        printf("%d\n", ans % 256);
    }
    return 0;
}

HDU - 4552 怪盗基德的挑战书 (后缀数组)

标签：des   style   color   io   os   ar   for   数据   sp   

原文地址：http://blog.csdn.net/u011345136/article/details/39700403