Codeforces Round #373 (Div. 2) B.Anatoly and Cockroaches

#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 1000010;
int n, x[2], y[2];
char s[N];

int main()
{
    scanf("%d %s", &n, s + 1);
    for (int i = 1; i <= n; i++) if (s[i] == 'r') x[i & 1]++; else
    y[i & 1]++;
    printf("%d", min(max(x[0], y[1]), max(x[1], y[0])));
    return 0;
}

#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
using namespace std;
int main()
{
    int n;
    while(cin>>n)
    {
        string s;
        cin>>s;
        int sum1=0,sum2=0;
        char pre=s[0];
        bool cnt=s[0]=='r'?true:false;
        for(int i=1;i<s.size();i++)
        {
            if(cnt)pre='r';
            else pre='b';
            if(s[i]==pre)
            {
                if(cnt)sum1++;
                else sum2++;
            }
            cnt=!cnt;
        }
        int res;
        res=min(sum1,sum2)+abs(sum1-sum2);

        sum1=0;  //b
        sum2=0;  //r
        pre=s[0];
        cnt=s[0]=='r'?false:true;
        if(cnt)sum1++;
        else sum2++;
        for(int i=1;i<s.size();i++)
        {
            if(cnt)pre='r';
            else pre='b';
            if(s[i]==pre)
            {
                if(cnt)sum2++;
                else sum1++;
            }
            cnt=!cnt;
        }
        res=min(res,min(sum1,sum2)+abs(sum1-sum2));
        cout<<res<<endl;
    }
}

大神代码 VS 我的代码