正常解法:

#include<iostream>
using namespace std;
int main(){
    int a,b;
    cin>>a>>b;
    cout<<(a*10+b)/19;
    return 0;
}

错解

#include<iostream>
#include<cstring>
#include<cstdio>
#include<cstring>
using namespace std;
int read(){
    int x=0,flag=1;
    char c=getchar();
    if(c=='-')flag=0,c=getchar();
    while(c!=' '&&c!='\n'&&c!='\r'){
        x=x*10+c-'0';
        c=getchar();
    }
    if(flag==0){
        return -x;
    }
    return x;
}
struct node {
    int data,rev,sum;
    node *son[2],*pre;
    bool judge();
    bool isroot();
    void pushdown();
    void update();
    void setson(node *child,int lr);
}lct[233];
int top,a,b;
node *getnew(int x){
    node *now=lct+ ++top;
    now->data=x;
    now->pre=now->son[1]=now->son[0]=lct;
    now->sum=0;
    now->rev=0;
    return now;
}
bool node::judge(){return pre->son[1]==this;}
bool node::isroot(){
    if(pre==lct)return true;
    return !(pre->son[1]==this||pre->son[0]==this);
}
void node::pushdown(){
    if(this==lct||!rev)return;
    swap(son[0],son[1]);
    son[0]->rev^=1;
    son[1]->rev^=1;
    rev=0;
}
void node::update(){sum=son[1]->sum+son[0]->sum+data;}
void node::setson(node *child,int lr){
    this->pushdown();
    child->pre=this;
    son[lr]=child;
    this->update();
}
void rotate(node *now)
{
    node *father=now->pre,*grandfa=father->pre;
    if(!father->isroot()) grandfa->pushdown();
    father->pushdown();now->pushdown();
    int lr=now->judge();
    father->setson(now->son[lr^1],lr);
    if(father->isroot()) now->pre=grandfa;
    else grandfa->setson(now,father->judge());
    now->setson(father,lr^1);
    father->update();now->update();
    if(grandfa!=lct) grandfa->update();
}
void splay(node *now){
    if(now->isroot())return;
    for(;!now->isroot();rotate(now))
    if(!now->pre->isroot())
    now->judge()==now->pre->judge()?rotate(now->pre):rotate(now);
}
node *access(node *now){
    node *last=lct;
    for(;now!=lct;last=now,now=now->pre)
    {
        splay(now);
        now->setson(last,1);
    }
    return last;
}
void changeroot(node *now){
    access(now)->rev^=1;
    splay(now);
}
void connect(node *x,node *y){
    changeroot(x);
    x->pre=y;
    access(x);
}
void cut(node *x,node *y){
    changeroot(x);
    access(y);
    splay(x);
    x->pushdown();
    x->son[1]=y->pre=lct;
    x->update();
}
int query(node *x,node *y){
    changeroot(x);
    node *now=access(y);
    return now->sum;
}
void write(int x) {
    if (x < 0){
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10);
    putchar(x % 10 + '0');
}
int main(){
    a=read(),b=read();
    node *A=getnew(a);
    node *B=getnew(b);
        connect(A,B);
        cut(A,B);
        connect(A,B);
    int money=query(A,B);
    for(int i=1;i<10;i++){
        node *Money=getnew(money);
        connect(A,Money);
        cut(A,Money);
        connect(A,Money);
        money=query(Money,A);
    }
    int i=0;
    while(money>19){
        node *I=getnew(i);
        node *One=getnew(1);
        node *Pencil=getnew(-19);
        node *Money=getnew(money);
        connect(Pencil,Money);
        cut(Pencil,Money);
        connect(Pencil,Money);
        connect(I,One);
        cut(I,One);
        connect(I,One);
        money=query(Money,Pencil);
        i=query(I, One);
    }
    write(i);
    return 0;
}

本蒟蒻也来发题解了qwq：

首先我们将 $a$ 元 $b$ 角转换为以角做单位的数值，之后除以 $1$ 元 $9$ 角（也就是 $19$ 角）：

#include <bits/stdc++.h>
using namespace std;
int a,b;
int main() {
    cin>>a>>b;
    a=a*10+b*1;
    cout<<a/19;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a,b;
    cin>>a>>b;
    a *= 10;
    a += b;
    cout<<a/19<<endl;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b;
	c=a*10+b;
	cout<<c/19<<endl;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
int a,b;
int main()
{
cin>>a>>b;
a=a*10+b;
cout<<a/19;
return 0;
}

#include<iostream>
using namespace std;
int main() {
    int a, b, m1, m2, num;
    cin >> a >> b;
    m1 = 10 * a + b;
    m2 = 10 * 1 + 9;
    num = m1 / m2;
    cout << num;
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main() {
    int a,b;
    cin>>a>>b;
    cout<<(a*10+b)/19<<endl;
    return 0;
}

依题意模拟即可

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

int main()
{
	ll a,b,to,my=19;
	cin>>a>>b;
	to=a*10+b;
	cout<<to/my;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
long long q,w,e,r,t,y,u,i,o,p,d,f,g,h,j,k,l,z,x,c,v,b,n,m;
char s;
long long a[100000],as[100000],asd[100000];
int main()
{
	cin>>x>>y;
	cout<<(x*10+y)/19;
    return 0;
}

#include<bits/stdc++.h>

using namespace std;

int main()

{

double a,b;

int c;

cin>>a>>b;

c=(a+b/10)/1.9;

cout<<c;

return 0; 

}

double a=0; double b=0; Scanner sc=new Scanner(System.in); for(int i=1;i<=2;i++) { System.out.print("\t"); a=sc.nextDouble(); b=sc.nextDouble(); double c=(a+b/10)/1.9; double d=(int)c; System.out.println(d);