C++ 代码

#include <iostream>
using namespace std;
const int N = 2e5 + 10;
char a[N]; // 数组模拟栈
int r = 0;

int main(){
    int n;
    string s;
    cin >> n >> s;

    for(char c : s){
        if(r == 0) {
            a[r ++] = c;
        }else{
            if(c == a[r - 1]) a[r ++] = c;
            else -- r;
        }
    }
    cout << r << endl;
    return 0;
}