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
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    ios::sync_with_stdio(false);

    int t;
    cin >> t;

    for (int test = 0; test < t; test++) {
        int numberOfCities;
        cin >> numberOfCities;

        string infectedCities;
        cin >> infectedCities;

        int i = 0;
        int leftIslandSize = 0, rightIslandSize = 0;
        while (i < infectedCities.size() && infectedCities[i] == '0') {
            leftIslandSize++;
            i++;
        }

        if (leftIslandSize == infectedCities.size()) {
            cout << 0 << endl;
            continue;
        }

        i = infectedCities.size() - 1;
        while (i >= 0 && infectedCities[i] == '0') {
            rightIslandSize++;
            i--;
        }

        vector<int> uninfectedIslands;
        i = leftIslandSize;
        int lastCityIndex = infectedCities.size() - 1 - rightIslandSize;

        while (i < lastCityIndex) {
            while (i < lastCityIndex && infectedCities[i] == '1') {
                i++;
            }

            int currentIslandSize = 0;

            while (i < lastCityIndex && infectedCities[i] == '0') {
                i++;
                currentIslandSize++;
            }

            if (currentIslandSize > 0) {
                uninfectedIslands.push_back(currentIslandSize);
            }

        }

        if (uninfectedIslands.size() == 0) {
            int result = leftIslandSize + rightIslandSize - 1;
            if (leftIslandSize == 0 || rightIslandSize == 0) {
                result++;
            }
            cout << numberOfCities - result << endl;
            continue;
        }

        sort(uninfectedIslands.begin(), uninfectedIslands.end(), greater<int>());

        if (leftIslandSize < rightIslandSize) {
            int tmp = leftIslandSize;
            leftIslandSize = rightIslandSize;
            rightIslandSize = tmp;
        }

        int day = 0;
        int citiesSaved = 0;
        bool leftUsed = false, rightUsed = false;

        for (int i = 0; i < uninfectedIslands.size(); i++) {
            if (!leftUsed) {
                if (uninfectedIslands[i] < 2 * leftIslandSize && leftIslandSize - day > 0) {
                    citiesSaved += leftIslandSize - day;
                    day++;
                    leftUsed = true;
                }
            }
            if (!rightUsed) {
                if (uninfectedIslands[i] < 2 * rightIslandSize && rightIslandSize - day > 0) {
                    citiesSaved += rightIslandSize - day;
                    day++;
                    rightUsed = true;
                }
            }
            
            int currentSavedCities = uninfectedIslands[i] - 2 * day;
            
            if (currentSavedCities > 1) {
                currentSavedCities--;
            }

            if (currentSavedCities < 1) {
                break;
            }
            citiesSaved += currentSavedCities;
            day += 2;
        }

        if (!leftUsed && leftIslandSize - day > 0) {
            citiesSaved += leftIslandSize - day;
            day++;        
        }
        if (!rightUsed && rightIslandSize - day > 0) {
            citiesSaved += rightIslandSize - day;
        }

        cout << numberOfCities - citiesSaved << endl;
    }
}