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  • [HAOI2016]找相同字符(后缀自动机)

    /*
    
    一个建立后缀自动机一个跑就行
    依旧是对于所有的祖先都有贡献
     
    
    */
    
    #include<cstdio>
    #include<algorithm>
    #include<cstring>
    #include<queue>
    #include<iostream>
    #define ll long long 
    #define mmp make_pair
    #define M 400010
    using namespace std;
    int read()
    {
    	int nm = 0, f = 1;
    	char c = getchar();
    	for(; !isdigit(c); c = getchar()) if(c == '-') f = -1;
    	for(; isdigit(c); c = getchar()) nm = nm * 10 + c - '0';
    	return nm * f;
    }
    int len[M], fa[M], ch[M][26], sz[M], f[M], g[M], tim[M], a[M], cnt = 1, lst = 1;
    char s[M]; 
    ll ans = 0;
    
    void insert(int c)
    {
    	int p = ++cnt, f = lst;
    	lst = p;
    	len[p] = len[f] + 1;
    	sz[p] = 1;
    	while(f && !ch[f][c]) ch[f][c] = p, f = fa[f];
    	if(!f) fa[p] = 1;
    	else
    	{
    		int q = ch[f][c];
    		if(len[q] == len[f] + 1) fa[p] = q;
    		else
    		{
    			int nq = ++cnt;
    			memcpy(ch[nq], ch[q], sizeof(ch[q]));
    			fa[nq] = fa[q];
    			len[nq] = len[f] + 1;
    			fa[q] = fa[p] = nq;
    			while(f && ch[f][c] == q) ch[f][c] = nq, f = fa[f];
    		}
    	}
    }
    int main()
    {
    	scanf("%s", s + 1);
    	int l = strlen(s + 1);
    	for(int i = 1; i <= l; i++) insert(s[i] - 'a');
    	for(int i = 1; i <= cnt; i++) tim[len[i]]++;
    	for(int i = 1; i <= cnt; i++) tim[i] += tim[i - 1];
    	for(int i = 1; i <= cnt; i++) a[tim[len[i]]--] = i;
    	for(int i = cnt; i >= 1; i--) sz[fa[a[i]]] += sz[a[i]];
    	scanf("%s", s + 1);
    	l = strlen(s + 1);
    	int now = 1, lt = 0;
    	for(int i = 1; i <= l; i++)
    	{
    		int c = s[i] - 'a';
    		if(ch[now][c]) lt++, now = ch[now][c];
    		else {
    			while(now && !ch[now][c]) now = fa[now];
    			if(!now) now = 1, lt = 0;
    			else lt = len[now] + 1, now = ch[now][c];
    		}
    		ans += 1ll * sz[now] * (lt - len[fa[now]]);
    		g[now]++;
    	}
    	for(int i = cnt; i >= 1; i--)
    	{
    		ans += 1ll * sz[a[i]] * f[a[i]] * (len[a[i]] - len[fa[a[i]]]);
    		f[fa[a[i]]] += f[a[i]] + g[a[i]];
    	}
    	cout << ans << "
    ";
    	return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/luoyibujue/p/10628633.html
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