题解 2B

#include <bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define N 100010
#define ll long long
#define reg register int
//#define int long long 

int n;
char s[N], sta[N], tem[N];

signed main()
{
	freopen("apstr.in", "r", stdin);
	freopen("apstr.out", "w", stdout);

	scanf("%s", s+1); n=strlen(s+1);
	int pos1=0, pos2=1;
	for (; pos2<=n; ++pos2) {
		if (s[pos2]=='P' && pos1 && sta[pos1]=='A') --pos1;
		else sta[++pos1]=s[pos2];
	}
	// cout<<"pos1: "<<pos1<<endl;
	n=pos1; pos1=0; pos2=1;
	for (; pos2<=n; ++pos2) {
		if (sta[pos2]=='P' && pos1 && tem[pos1]=='P') --pos1;
		else tem[++pos1]=sta[pos2];
	}
	printf("%d\n", pos1);

	return 0;
}