Codeforces #985F: Isomorphic Strings 题解

感觉虽然是edu round的倒数第二题但还蛮简单的
我们分析那个同构的定义，可以理解为“该一样的字符要一样，该不一样的字符要不一样”，那么对于每一种字符我们想一种办法来表示他在子串中所有的出现位置（像一张有黑点的纸条），然后看看两个串能不能配对就好
把一个01串转换成一个数，我刚开始想的是高精度用$2^n$表示，然而复杂度是炸的，然后我发现自己蠢了，用字符串哈希就可以了
为了保险我写了双哈希

#include <cstdio>
#include <iostream>
#include <cstring>
#include <string>
#include <cstdlib>
#include <utility>
#include <cctype>
#include <algorithm>
#include <bitset>
#include <set>
#include <map>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#define LL long long
#define LB long double
#define x first
#define y second
#define Pair pair<int,int>
#define pb push_back
#define pf push_front
#define mp make_pair
#define LOWBIT(x) x & (-x)
using namespace std;

const int MOD=1e9+7;
const LL LINF=2e16;
const int INF=1e9;
const int magic=348;
const double eps=1e-10;
const double pi=3.14159265;

inline int getint()
{
    char ch;int res;bool f;
    while (!isdigit(ch=getchar()) && ch!='-') {}
    if (ch=='-') f=false,res=0; else f=true,res=ch-'0';
    while (isdigit(ch=getchar())) res=res*10+ch-'0';
    return f?res:-res;
}

char s[200048];
vector<int> pos[48];
int n,q;

const int p1=998244353,p2=1004535809;
const int m1=1e9+7,m2=1e9+9;
LL hsh1[48][200048],hsh2[48][200048],P1[200048],P2[200048];
inline void init_hash()
{
    int i,j;P1[0]=P2[0]=1;
    for (i=1;i<=n;i++) P1[i]=(P1[i-1]*p1)%m1,P2[i]=(P2[i-1]*p2)%m2;
    for (i=1;i<=26;i++)
        for (j=1;j<=n;j++)
        {
            hsh1[i][j]=(hsh1[i][j-1]*p1+(s[j]=='a'+i-1)*3)%m1;
            hsh2[i][j]=(hsh2[i][j-1]*p2+(s[j]=='a'+i-1)*3)%m2;
        }
}

inline LL mod1(LL x) {while (x>=m1) x-=m1;while (x<0) x+=m1;return x;}
inline LL mod2(LL x) {while (x>=m2) x-=m2;while (x<0) x+=m2;return x;}
inline LL gethash1(int type,int left,int right) {return mod1(hsh1[type][right]-(hsh1[type][left-1]*P1[right-left+1])%m1);}
inline LL gethash2(int type,int left,int right) {return mod2(hsh2[type][right]-(hsh2[type][left-1]*P2[right-left+1])%m2);}

LL val1[48],val2[48];

int main ()
{
    n=getint();q=getint();scanf("%s",s+1);
    init_hash();
    int s1,s2,len,i;
    while (q--)
    {
        s1=getint();s2=getint();len=getint();
        bool ans=true;
        memset(val1,0,sizeof(val1));memset(val2,0,sizeof(val2));
        for (i=1;i<=26;i++) val1[i]=gethash1(i,s1,s1+len-1),val2[i]=gethash1(i,s2,s2+len-1);
        sort(val1+1,val1+27);sort(val2+1,val2+27);
        for (i=1;i<=26;i++) if (val1[i]!=val2[i]) ans=false;
        memset(val1,0,sizeof(val1));memset(val2,0,sizeof(val2));
        for (i=1;i<=26;i++) val1[i]=gethash2(i,s1,s1+len-1),val2[i]=gethash2(i,s2,s2+len-1);
        sort(val1+1,val1+27);sort(val2+1,val2+27);
        for (i=1;i<=26;i++) if (val1[i]!=val2[i]) ans=false;
        if (ans) puts("YES"); else puts("NO");
    }
    return 0;
}