Dutch Flag Problem

 

#include <iostream>
#include <vector>
using namespace std;


void dutchFlag(vector<int>& v, int pivot) {
    int smaller = 0;
    int equal = 0;
    int larger = v.size() - 1;
    while (equal < larger) {
        if (v[equal] < pivot) {
            swap(v[smaller++], v[equal++]);
        }
        else if (v[equal] == pivot) {
            equal++;
        }
        else {
            swap(v[larger--], v[equal]);
        }
    }
}

/*void dutchFlag(vector<int>& v, int pivot) {
    int smaller = 0;
    for (int i = 0; i < v.size(); i++) {
        if (v[i] < pivot) {
            swap(v[i], v[smaller++]);
        }
    }
    int larger = v.size() - 1;
    for (int i = v.size() - 1; i >= 0 && v[i] >= pivot; i--) {
        if (v[i] > pivot) {
            swap(v[i], v[larger--]);
        }
    }
}*/

/*
void dutchFlag(vector<int>& v, int pivot) {
    for (int i = 0; i < v.size(); i++) {
        for (int j = i + 1; j < v.size(); j++) {
            if (v[j] < pivot) {
                swap(v[i], v[j]);
                break;
            }
        }
    }
    for (int i = v.size() - 1; i >= 0 && v[i] >= pivot; i--) {
        for (int j = i - 1; j >= 0 && v[i] >= pivot; j--) {
            if (v[j] > pivot) {
                swap(v[i], v[j]);
                break;
            }
        }
    }
}*/

int main()
{
    vector<int> v = { 1, 0, 0 , 2, 1, 2, 0 };
    dutchFlag(v, 1);
    for (auto i = v.begin(); i != v.end(); i++)
        cout << *i << " ";
    return 0;
}