Codeforces 242(DIV 2) A题

水题：直接模拟即可,次数cnt = abs（cnt1-cnt2）/2;

#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
int main(){
    string s;
    int n, ans;
    while(~scanf("%d", &n)){
        s.clear();
        cin >> s;
        int cnt1 = 0, cnt2 = 0;
        for(int i = 0;i < n;i ++){
            if(s[i] == 'x') cnt1 ++;
            else cnt2 ++;
        }
        cout << abs(cnt1-cnt2)/2 << endl;
        if(cnt1 == cnt2) cout << s << endl;
        else if(cnt1 > cnt2){
            int cnt = 0;
            for(int i = 0;i < n;i ++){
                if(s[i] == 'x') s[i] = 'X', cnt++;
                if(cnt == (cnt1-cnt2)/2){
                    cout << s << endl;
                    break;
                }
            }
        }else{
            int cnt = 0;
            for(int i = 0;i < n;i ++){
                if(s[i] == 'X') s[i] = 'x', cnt++;
                if(cnt == (cnt2-cnt1)/2){
                    cout << s << endl;
                    break;
                }
            }
        }
    }
    return 0;
}