POJ 3415 Common Substrings 后缀数组+并查集

后缀数组，看到网上很多题解都是单调栈，这里提供一个不是单调栈的做法，

首先将两个串 连接起来求height   求完之后按height值从大往小合并。  height值代表的是  sa[i]和sa[i-1] 的公共前缀长度，那么每次合并就是合并  i和i-1 那么在合并小的时候公共前缀更大的肯定已经都合并在一起，那么就可以直接统计了。  

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<time.h>
#include<string>
#define cl(a,b)	memset(a,b,sizeof(a))
#define max(x,y) ((x)>(y)?(x):(y))
#define min(x,y) ((x)<(y)?(x):(y))
#define REP(i,n) for(int i=0;i<n;++i)
#define REP1(i,a,b) for(int i=a;i<=b;++i)
#define REP2(i,a,b) for(int i=a;i>=b;--i)
#define MP make_pair
#define LL long long
#define ULL unsigned long long
#define X first
#define Y second
using namespace std;

const int MAXN =  200050;

struct SuffixArray{
    int wa[MAXN];
    int wb[MAXN];
    int wv[MAXN];
    int ws[MAXN];

    int sa[MAXN];
    int rank[MAXN];
    int height[MAXN];
    int r[MAXN];
    int n;
    int m;

    void input(int *val, int len, int Max){
        for (int i = 0;i < len;i++)
            r[i] = val[i];
        r[len] = 0;
        n = len;
        m = Max;
        calSa();
        calHeight();
    }

    int cmp(int *r, int a, int b, int l){
        return (r[a] == r[b] && r[a + l] == r[b + l]);
    }

    void calSa(){
        int i, j, p, *x = wa, *y = wb, *t;
        for (i = 0;i < m;i++) ws[i] = 0;
        for (i = 0;i < n + 1;i++) ws[x[i] = r[i]]++;
        for (i = 1;i < m;i++) ws[i] += ws[i - 1];
        for (i = n;i >= 0;i--) sa[--ws[x[i]]] = i;
        for (j = 1, p = 1;p < n + 1;j *= 2, m = p){
            for (p = 0, i = n - j + 1;i < n + 1;i++) y[p++] = i;
            for (i = 0;i < n + 1;i++) if (sa[i] >= j) y[p++] = sa[i] - j;
            for (i = 0;i < n + 1;i++) wv[i] = x[y[i]];
            for (i = 0;i < m;i++) ws[i] = 0;
            for (i = 0;i < n + 1;i++) ws[wv[i]]++;
            for (i = 1;i < m;i++) ws[i] += ws[i - 1];
            for (i = n;i >= 0;i--) sa[--ws[wv[i]]] = y[i];
            for (t = x, x = y, y = t, p = 1, x[sa[0]] = 0, i = 1; i < n + 1;i++)
                x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
        }
    }

    void calHeight(){
        int i, j, k = 0;
        for (i = 1;i <= n;i++) rank[sa[i]] = i;
        for (i = 0;i < n;height[rank[i++]] = k)
            for (k?k--:0, j = sa[rank[i]- 1];r[i + k] == r[j + k];k++);
    }

}SA;
char s1[MAXN],s2[MAXN];
int s[MAXN];
vector<int>e[MAXN];
int id[MAXN];
int x[MAXN],y[MAXN];
int fa[MAXN];
int getfa(int x)
{
	if(fa[x]==x)return x;
	else
		return fa[x]=getfa(fa[x]);
}
int main()
{
	int k;
	while(scanf("%d",&k)&&k)
	{
		int h=0,len1,len2;
		scanf(" %s %s",s1,s2);
		len1=strlen(s1);
		len2=strlen(s2);
		for(int i=0;i<len1;++i)
		{
			id[h]=0;
			s[h++]=s1[i];
		}
		s[h++]=1;
		for(int i=0;i<len2;++i)
		{
			id[h]=1;
			s[h++]=s2[i];
		}
		SA.input(s,h,500);
//		for(int i=0;i<=h;++i)
//			printf("%d %d %d\n",i,SA.sa[i],SA.height[i]);
		for(int i=0;i<=h;++i)
			e[i].clear();
		for(int i=1;i<=h;++i)
		{
			e[SA.height[i]].push_back(i);
		}
		for(int i=0;i<=h;++i)
		{
			fa[i]=i;
			if(id[SA.sa[i]]==0)//这里要用sa来判断原先属于哪个串
				x[i]=1,y[i]=0;
			else
				x[i]=0,y[i]=1;
		}
		LL ans=0;
		for(int i=h;i>=k;--i)
		{
			for(int j=0;j<e[i].size();++j)
			{
				int u=e[i][j];
				int f1=getfa(u);
				int f2=getfa(u-1);
//				printf("%d %d\n",f1,f2);
				if(f1!=f2){
					ans-=(LL)x[f2]*y[f2]*(i-k+1);//减去原先的贡献值
					ans-=(LL)x[f1]*y[f1]*(i-k+1);//减去原先的贡献值
					fa[f1]=f2;
					x[f2]+=x[f1];
					y[f2]+=y[f1];
					ans+=(LL)x[f2]*y[f2]*(i-k+1);//加上新的
				}
			}
		}
		printf("%I64d\n",ans);
	}
}