codeforces Polo the Penguin and Strings 思维问题代码链接

#include<stdio.h>
#include<string.h>
char a[1200000];
int main()
{
int n,m;
while(scanf("%d%d",&n,&m)!=EOF){
if(n<m){printf("-1\n");continue;}
if((m==1)&&(n>1)){printf("-1\n");continue;}
if((m==1)&&(n==1)){printf("a\n");continue;}
memset(a,'0',sizeof(char)*(n+10));
int sub=m-2,add=m-2;;
a
='\0';
for(int i=n-1;i>=n-1-sub+1;i--){
a[i]='b'+add;
add--;
}
int flag=0,i=0;
while(a[i]=='0'){
if(flag==0)a[i]='a';
else a[i]='b';
flag=1-flag;
i++;
}
printf("%s\n",a);
}

}