C. String Transformation
time limit per test1 second
memory limit per test256 megabytes
inputstandard input
outputstandard output
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
inputCopy
aacceeggiikkmmooqqssuuwwyy
outputCopy
abcdefghijklmnopqrstuvwxyz
inputCopy
thereisnoanswer
outputCopy
-1
读懂了题意，从字母a开始一次判断当前第i个字母是否可以改变成所需的字母，若不能后移，若可以改变当前字母，字母++；
#include<iostream>
#include<string.h>
using namespace std;
int main()
{
char a[106];
scanf("%s",a);//97-122
char x;
x='a';
int ans=0;
int flag;
for(int i=0;i<strlen(a);i++)
{
if(a[i]<=x)
{
a[i]=x;
x++;
ans++;
}
if(ans==26)
{
flag=1;
break;
}
}
if(flag==1)
printf("%s",a);
else
cout<<-1;
}