SPOJ 题目694 Distinct Substrings（后缀数组，求不同的子串个数）

DISUBSTR - Distinct Substrings

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Given a string, we need to find the total number of its distinct substrings.

Input

T- number of test cases. T<=20;

Each test case consists of one string, whose length is <= 1000

Output

For each test case output one number saying the number of distinct substrings.

Example

Sample Input:

2

CCCCC

ABABA

Sample Output:

5

9

Explanation for the testcase with string ABABA:

len=1 : A,B

len=2 : AB,BA

len=3 : ABA,BAB

len=4 : ABAB,BABA

len=5 : ABABA

Thus, total number of distinct substrings is 9.

ac代码

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
using namespace std;
int s[2002];
char str[2002];
int sa[2002],t1[2002],t2[2002],c[2002];
int rank[2002],height[2002];
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;
    }
}
int main()
{
	int t;
	scanf("%d",&t);
	while(t--)
	{
		int i;
		scanf("%s",str);
		int len=strlen(str);
		for(i=0;i<len;i++)
		{
			s[i]=str[i];
		}
		s[len]=0;
		build_sa(s,len+1,128);
		getHeight(s,len);
		long long ans=(len)*(len+1)/2;
		for(i=1;i<=len;i++)
		{
			ans-=height[i];
		}
		printf("%lld\n",ans);
	}
}

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