hackerrank: sort by swaps

01. Arrays and strings/hackerrank/order_by_swaps.cpp

@@ -0,0 +1,133 @@
+/*
+
+# Minimum Swaps 2
+
+https://www.hackerrank.com/challenges/minimum-swaps-2/problem
+
+You are given an unordered array consisting of consecutive integers
+
+[1, 2, 3, ..., n] without any duplicates. You are allowed to swap any two elements. You need to find the minimum number of swaps required to sort the array in ascending order.
+
+For example, given the array arr = [7,1,3,2,4,5,6] we perform the following steps:
+
+i   arr                         swap (indices)
+0   [7, 1, 3, 2, 4, 5, 6]   swap (0,3)
+1   [2, 1, 3, 7, 4, 5, 6]   swap (0,1)
+2   [1, 2, 3, 7, 4, 5, 6]   swap (3,4)
+3   [1, 2, 3, 4, 7, 5, 6]   swap (4,5)
+4   [1, 2, 3, 4, 5, 7, 6]   swap (5,6)
+5   [1, 2, 3, 4, 5, 6, 7]
+
+It took 5 swaps to sort the array.
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+vector<string> split_string(string);
+
+// Complete the minimumSwaps function below.
+int minimumSwaps2(vector<int> arr)
+{
+    int swaps = -1;
+    vector<bool> vis(arr.size(), false);
+    for (size_t i = 0; i < arr.size(); i++)
+    {
+        if (vis[i] || arr[i] == i + 1)
+        {
+            vis[i] = true;
+            continue;
+        }
+        int val = arr[i];
+        while (!vis[val - 1])
+        {
+            vis[val - 1] = true;
+            val = arr[val - 1];
+            swaps++;
+        }
+    }
+    return swaps;
+}
+
+// numbers don't necessarily need to be consecutive, could be 1,2,3,77,88,6
+int minimumSwaps(vector<int> arr){
+    int first = 0;
+    int last = arr.size() - 1;
+    int swaps = 0;
+    while (first < last){
+        while (arr[first] == first + 1 && first < last){
+            first++;
+        }
+        if (first < last){
+            int temp = arr[arr[first] - 1];
+            arr[arr[first] - 1] = arr[first];
+            arr[first] = temp;
+            swaps++;
+        }
+    }
+    return swaps;
+}
+
+int main()
+{
+    ofstream fout(getenv("OUTPUT_PATH"));
+
+    int n;
+    cin >> n;
+    cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+    string arr_temp_temp;
+    getline(cin, arr_temp_temp);
+
+    vector<string> arr_temp = split_string(arr_temp_temp);
+
+    vector<int> arr(n);
+
+    for (int i = 0; i < n; i++)
+    {
+        int arr_item = stoi(arr_temp[i]);
+
+        arr[i] = arr_item;
+    }
+
+    int res = minimumSwaps(arr);
+
+    fout << res << "\n";
+
+    fout.close();
+
+    return 0;
+}
+
+vector<string> split_string(string input_string)
+{
+    string::iterator new_end = unique(input_string.begin(), input_string.end(), [](const char &x, const char &y) {
+        return x == y and x == ' ';
+    });
+
+    input_string.erase(new_end, input_string.end());
+
+    while (input_string[input_string.length() - 1] == ' ')
+    {
+        input_string.pop_back();
+    }
+
+    vector<string> splits;
+    char delimiter = ' ';
+
+    size_t i = 0;
+    size_t pos = input_string.find(delimiter);
+
+    while (pos != string::npos)
+    {
+        splits.push_back(input_string.substr(i, pos - i));
+
+        i = pos + 1;
+        pos = input_string.find(delimiter, i);
+    }
+
+    splits.push_back(input_string.substr(i, min(pos, input_string.length()) - i + 1));
+
+    return splits;
+}