codeforce A. AB Balance

2021-11-09 21:01:42 阅读：417 来源： 互联网

标签：AB string number ba codeforce test Balance BA

A. AB Balance

time limit per test2 seconds
memory limit per test256 megabytes
inputstandard input
outputstandard output
You are given a string s of length n consisting of characters a and/or b.

Let AB(s) be the number of occurrences of string ab in s as a substring. Analogically, BA(s) is the number of occurrences of ba in s as a substring.

In one step, you can choose any index i and replace si with character a or b.

What is the minimum number of steps you need to make to achieve AB(s)=BA(s)?

Reminder:

The number of occurrences of string d in s as substring is the number of indices i (1≤i≤|s|−|d|+1) such that substring sisi+1…si+|d|−1 is equal to d. For example, AB(aabbbabaa)=2 since there are two indices i: i=2 where aabbbabaa and i=6 where aabbbabaa.

Input
Each test contains multiple test cases. The first line contains the number of test cases t (1≤t≤1000). Description of the test cases follows.

The first and only line of each test case contains a single string s (1≤|s|≤100, where |s| is the length of the string s), consisting only of characters a and/or b.

Output
For each test case, print the resulting string s with AB(s)=BA(s) you’ll get making the minimum number of steps.

If there are multiple answers, print any of them.

Example
inputCopy
4
b
aabbbabaa
abbb
abbaab
outputCopy
b
aabbbabaa
bbbb
abbaaa
Note
In the first test case, both AB(s)=0 and BA(s)=0 (there are no occurrences of ab (ba) in b), so can leave s untouched.

In the second test case, AB(s)=2 and BA(s)=2, so you can leave s untouched.

In the third test case, AB(s)=1 and BA(s)=0. For example, we can change s1 to b and make both values zero.

In the fourth test case, AB(s)=2 and BA(s)=1. For example, we can change s6 to a and make both values equal to 1.

题目大意：有一串由a，b组成的字符串，一次操作可以将a换成b或者将b换成a，至少多少次操作可以是字符串中的ab字串的数量等于ba字串的数量，输出的是变换后的字符串

思路：因为是有a，b组成的所以，ab的数量与ba的数量要不相同，要不相差一，如果字符串以a开头那么，这个字符串中的n(ab)>=n(ba);所以如果n(ab)==n(ba)，直接输出原始串，如果n(ab)>n(ba),把开头的a换成b就可以，然后在输出，b开头同理

代码：

#include <iostream>
using namespace std;
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        string s;
        cin>>s;
        int a=0,b=0;
        for(int i=1;i<s.size();i++)
        {
            if(s[i]=='a'&&s[i-1]=='b') b++;
            else if(s[i]=='b'&&s[i-1]=='a') a++;
        }
        if(a==b) cout<<s<<endl;
        else if(a>b)
        {
            if(s[0]=='a') s[0]='b';
            cout<<s<<endl;
        }
        else if(b>a)
        {
            if(s[0]=='b') s[0]='a';
            cout<<s<<endl;
        }
    }
    return 0;
}

标签：AB,string,number,ba,codeforce,test,Balance,BA
来源： https://blog.csdn.net/weixin_51996479/article/details/121236503

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codeforce A. AB Balance

A. AB Balance