CodeForces 709C Letters Cyclic Shift

贪心。

肯定是两个$a$之间的那些字符都$-1$，没有$a$就全部$-1$。如果输入的串全是$a$，那么把最后一个$a$改成$z$。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0),eps=1e-6;
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}
template <class T>
inline void read(T &x)
{
    char c = getchar(); x = 0;while(!isdigit(c)) c = getchar();
    while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar();  }
}

const int maxn=100010;
char s[maxn]; bool flag;

int main()
{
    scanf("%s",s);
    for(int i=0;s[i];i++)
    {
        if(s[i]=='a')
        {
            if(flag==0) continue;
            else break;
        }
        s[i]--; flag=1;
    }

    if(flag==0)
    {
        int len=strlen(s);
        s[len-1]='z';
    }
    printf("%s\n",s);

    return 0;
}