給你A B兩個串，讓你切B串兩刀，問你能否把切開的三個串拼成A。

哈希顯然。

#include<cstdio>
#include<cstring>
using namespace std;
typedef unsigned long long ull;
const ull MOD1=2000000011;
const ull MOD2=1000000007;
const ull base1=10007;
const ull base2=10009;
int n;
char a[10010],b[10010]/*,d[10010],e[10010]*/;
ull b1s[10010],b2s[10010];
ull hs[3][10010];
const int c[7][4]={{0,0,0,0},{0,1,2,3},{0,1,3,2},{0,2,1,3},{0,2,3,1},{0,3,1,2},{0,3,2,1}};
int main(){
	b1s[0]=b2s[0]=1;
	scanf("%s%s",b+1,a+1);
//	memcpy(d,b,sizeof(b));
//	memcpy(e,a,sizeof(a));
	n=strlen(a+1);
	for(int i=1;i<=n;++i){
		b1s[i]=b1s[i-1]*base1%MOD1;
		b2s[i]=b2s[i-1]*base2%MOD2;
	}
	ull hs2[3]={0};
	for(int i=1;i<=n;++i){
		if(a[i]<=‘Z‘){
			a[i]+=32;
		}
		if(b[i]<=‘Z‘){
			b[i]+=32;
		}
		hs2[1]=(hs2[1]*base1%MOD1+b[i]-‘a‘)%MOD1;
		hs2[2]=(hs2[2]*base2%MOD2+b[i]-‘a‘)%MOD2;
		hs[1][i]=(hs[1][i-1]*base1%MOD1+a[i]-‘a‘)%MOD1;
		hs[2][i]=(hs[2][i-1]*base2%MOD2+a[i]-‘a‘)%MOD2;
	}
	ull hs1[3][4];
	int len[4];
	len[0]=0;
	for(int i=1;i<=n-2;++i){
		for(int j=i+1;j<=n-1;++j){
			len[1]=i;
			len[2]=j-i;
			len[3]=n-j;
			
			hs1[1][1]=hs[1][i];
			hs1[1][2]=(hs[1][j]-hs[1][i]*b1s[len[2]]%MOD1+MOD1)%MOD1;
			hs1[1][3]=(hs[1][n]-hs[1][j]*b1s[len[3]]%MOD1+MOD1)%MOD1;
			hs1[2][1]=hs[2][i];
			hs1[2][2]=(hs[2][j]-hs[2][i]*b2s[len[2]]%MOD2+MOD2)%MOD2;
			hs1[2][3]=(hs[2][n]-hs[2][j]*b2s[len[3]]%MOD2+MOD2)%MOD2;
			
			for(int k=1;k<=6;++k){
				if(((hs1[1][c[k][1]]*b1s[len[c[k][2]]+len[c[k][3]]]%MOD1+hs1[1][c[k][2]]*b1s[len[c[k][3]]]%MOD1)%MOD1+hs1[1][c[k][3]])%MOD1 == hs2[1] && 
				((hs1[2][c[k][1]]*b2s[len[c[k][2]]+len[c[k][3]]]%MOD2+hs1[2][c[k][2]]*b2s[len[c[k][3]]]%MOD2)%MOD2+hs1[2][c[k][3]])%MOD2 == hs2[2]){
					puts("YES");
					for(int l=1;l<=3;++l){
						if(c[k][l]==1){
							for(int m=1;m<=len[1];++m){
								putchar(a[m]);
							}
						}
						else if(c[k][l]==2){
							for(int m=len[1]+1,mm=1;mm<=len[2];++m,++mm){
								putchar(a[m]);
							}
						}
						else{
							for(int m=len[1]+len[2]+1,mm=1;mm<=len[3];++m,++mm){
								putchar(a[m]);
							}
						}
						puts("");
					}
					return 0;
				}
			}
			
		}
	}
	puts("NO");
	return 0;
}

【枚舉】【字符串哈希】Gym - 101164K - Cutting