1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
#include <iostream>
#include <vector>
#include <string>
using namespace std;

struct Block {
    int len, dec;
};

void vector_pop(vector<Block>&V, int i) {
    swap(V[i], V.back());
    V.pop_back();
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t;
    cin >> t;
    while (t--) {
        int n;
        string str;
        cin >> n >> str;
        
        //build blocks
        vector<Block>B;
        int acc = 0;
        for (int i = 0; i < n; i++)
            if (str[i]=='0')
                acc++;
            else if(acc) {
                B.push_back(Block{.len=acc, .dec=2});
                acc = 0;
            }
        if (acc)
            B.push_back(Block{.len=acc, .dec=2});
        
        if (str.front()=='0')
            B.front().dec--;
        if (str.back()=='0')
            B.back().dec--;
        
        if (B.size()==1 && B[0].dec == 0) {
            cout << "0\n";
            continue;
        }

        int vac = 0;
        while (!B.empty()) {
            //find biggest
            int biggest_in_danger_i, biggest_in_danger_points = -1000;
            for (int i = 0; i < (int)B.size(); i++) {
                int points = B[i].len - 2*B[i].dec;
                if (points > biggest_in_danger_points) {
                    biggest_in_danger_i = i;
                    biggest_in_danger_points = points;
                }
            }
            
            //do it
            vac++;
            B[biggest_in_danger_i].dec--;
            B[biggest_in_danger_i].len--;
            if (B[biggest_in_danger_i].dec == 0 || B[biggest_in_danger_i].len == 0) {
                vac += B[biggest_in_danger_i].len;
                vector_pop(B, biggest_in_danger_i);
            }

            //virus propagate
            for (int i = 0; i < (int)B.size();) {
                B[i].len -= B[i].dec;
                if (B[i].len <= 0)
                    vector_pop(B, i);
                else
                    i++;
            }
        }
        
        cout << n - vac << endl;
    }

    return 0;
}