希望有大佬能详细讲下题目中提到的问题

我知道我下面这份代码 本地全过 而洛谷全WA是由这个原因引起的 但我不太清楚为什么 和 怎么 改

#include<iostream>
#include<cstdio> 
using namespace std;
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<<1)+(x<<3)+(ch^48),ch=getchar();
    return x*f;
}
int num;
int work1(int t)    //  这个函数将t转换成整形输出
{
	int k=0;
	string s;
	while(t)
	{
		k++;
		s+=(t%10+'0');
		t/=10;
	}
	for(int i=s.size()-1;i>=0;i--) printf("%c",s[i]);
	return k;
} 
int main()
{
	int n=read(),x,y;
	char pre;
	for(int i=1;i<=n;i++)
	{
		char c=getchar();
		x=read(),y=read();
		num=2;
		if(c=='a') 
		{
			num+=work1(x);
			printf("+");
			num+=work1(y);
			printf("=");
			num+=work1(x+y);
			printf("\n%d\n",num);
			pre=c;
		}
		else if(c=='c') 
		{
			num+=work1(x);
			printf("*");
			num+=work1(y); 
			printf("=");
			num+=work1(x*y);
			printf("\n%d\n",num);
			pre=c;
		}
		else if(c=='b') 
		{
			num+=work1(x);
			printf("-");
			num+=work1(y);
			printf("=");
			int m=x-y;
			if(m<0)
			{
				num++;
				printf("-");
				m=-m;
			}
			num+=work1(m);
			printf("\n%d\n",num);
			pre=c;
		}
		else
		{
			int t=x,num2=0,p=1;
			while(t)    //  计算录的x有多少位 
			{
				num2++;
				t/=10;
			}
			for(int i=1;i<=num2;i++) p*=10;
			x=x+(c-'0')*p;
			if(pre=='a') 
			{
				num+=work1(x);
				printf("+");
				num+=work1(y);
				printf("=");
				num+=work1(x+y);
				printf("\n%d\n",num);
			}
			else if(pre=='c') 
			{
				num+=work1(x);
				printf("*");
				num+=work1(y); 
				printf("=");
				num+=work1(x*y);
				printf("\n%d\n",num);
			}
			else if(pre=='b') 
			{
				num+=work1(x);
				printf("-");
				num+=work1(y);
				printf("=");
				int m=x-y;
				if(m<0)
				{
					num++;
					printf("-");
					m=-m;
				}
				num+=work1(m);
				printf("\n%d\n",num);
			}
		}
	}
	return 0;
}
/*
1
a 64 46
275 125
c 11 99
b 46 64
46 64
c 11 99
11 99 
*/

来个daloa救救我