题目链接：点这里！！！！
题意：（简单易懂自己看）
题解：直接kmp,但是要注意在+号前面的字符串指针一定要指到最后！！！
代码：
#include<cstdio>
#include<cstring>
#include<iostream>
#include<sstream>
#include<algorithm>
#include<vector>
#include<bitset>
#include<set>
#include<queue>
#include<stack>
#include<map>
#include<cstdlib>
#include<cmath>
#define PI 2*asin(1.0)
#define LL long long
#define pb push_back
#define pa pair<int,int>
#define clr(a,b) memset(a,b,sizeof(a))
#define lson lr<<1,l,mid
#define rson lr<<1|1,mid+1,r
#define bug(x) printf("%d++++++++++++++++++++%d\n",x,x)
#define key_value ch[ch[root][1]][0]C:\Program Files\Git\bin
const int MOD = 10007;
const int N = 1e5+15;
const int maxn = 1e4+1000;
const int letter = 130;
const int INF = 1e17;
const double pi=acos(-1.0);
const double eps=1e-8;
using namespace std;
inline int read()
{
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}
char a[N],b[N];
int f[N];
int lena,lenb;
void getfail(char *p,int *f,int n){
f[0]=-1;f[1]=0;
for(int i=1;i<n;i++){
int j=f[i];
while(j&&p[i]!=p[j]) j=f[j];
f[i+1]=p[i]==p[j]?j+1:0;
}
}
int solve(char *s,char *p){ ///p->next s+p
int lenp=strlen(p),lens=strlen(s);
getfail(p,f,lenp);
int i=0,j=0;
while(i<lenp&&j<lens){
if(i==-1||p[i]==s[j])++i,++j;
else i=f[i];
}
if(j==lens) return i;
return 0;
}
int main(){
while(scanf("%s%s",a,b)!=EOF){
lena=strlen(a),lenb=strlen(b);
///a+b
int x=solve(a,b);
///b+a
int y=solve(b,a);
if(x>y||(x==y&&strcmp(a,b)<0)){
printf("%s",a);
for(int i=x;i<lenb;i++) printf("%c",b[i]);
printf("\n");
}
else {
printf("%s",b);
for(int i=y;i<lena;i++) printf("%c",a[i]);
printf("\n");
}
}
return 0;
}