CodeForces 709C Letters Cyclic Shift (水题)

题意：给定一个字符串，让你把它的一个子串字符都减1，使得总字符串字典序最小。

析：由于这个题是必须要有一个字串，所以你就要注意这个只有一个字符a的情况，其他的就从开始减 1，如果碰到a了就不减了，如果到最后一位了还没开始减，

就减最后一位。

代码如下：

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>
#include <vector>
#include <map>
#include <cctype>
#include <cmath>
#include <stack>
#define freopenr freopen("in.txt", "r", stdin)
#define freopenw freopen("out.txt", "w", stdout)
using namespace std;

typedef long long LL;
typedef pair<int, int> P;
const int INF = 0x3f3f3f3f;
const double inf = 0x3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int maxn = 1e5 + 5;
const int mod = 1e8;
const char *mark = "+-*";
const int dr[] = {-1, 0, 1, 0, 1, 1, -1, -1};
const int dc[] = {0, 1, 0, -1, -1, 1, 1, -1};
int n, m;
const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
inline int Min(int a, int b){ return a < b ? a : b; }
inline int Max(int a, int b){ return a > b ? a : b; }
inline LL Min(LL a, LL b){ return a < b ? a : b; }
inline LL Max(LL a, LL b){ return a > b ? a : b; }
inline bool is_in(int r, int c){
    return r >= 0 && r < n && c >= 0 && c < m;
}
char s[maxn];

int main(){
    while(scanf("%s", s) == 1){
        int len = strlen(s);
        int ok = false;
        for(int i = 0; i < len; ++i){
            if(s[i] =='a' && ok)  break;
            if(i == len-1 && !ok){
                s[i] = (s[i]-'a'+25) % 26 + 'a';
                break;
            }
            if(s[i] != 'a'){
                ok = true;
                --s[i];
            }
        }
        printf("%s\n", s);
    }
    return 0;
}