【bzoj3450】 Tyvj1952 Easy

[code]#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<=b;i++)

int n;
char st[300001];
long double l[300001] , f[300001];

int main() {
    scanf("%d" , &n);
    scanf("%s" , st + 1);
    rep(i , 1 , n) {
        if (st[i] == 'o')
            l[i] = l[i - 1] + 1 , f[i] = f[i - 1] + (l[i] * 2 - 1);
        else if (st[i] == 'x')
            l[i] = 0 , f[i] = f[i - 1];
        else if (st[i] == '?')
            l[i] = (l[i - 1] + 1) / 2 , f[i] = f[i - 1] + (l[i - 1] + 0.5);
    }
    printf("%.4Lf\n" , f
);
    return 0;
}