Added minimum swaps to make arrays equal

src/algorithms/sorting/minimum_swaps.h

@@ -0,0 +1,65 @@
+#ifndef MINIMUM_SWAPS_H
+#define MINIMUM_SWAPS_H
+
+#ifdef __cplusplus
+#include <iostream>
+#include <vector>
+#include <cassert>
+#include <map>
+#endif
+
+/**
+* @brief minimum swaps function.
+* It computes the minimum swaps to make a equal to b
+* @param a: vector<int>
+* @param b: vector<int>
+* @return int: the minimum number of swaps to make array a equal to array b
+*/
+int minimum_swaps(std::vector<int> &a, std::vector<int> &b) {
+    assert(a.size() == b.size());
+    int n = int(a.size());
+    auto solve = [&](std::vector<int> &arr) -> int {
+        std::vector<std::pair<int, int> > positions;
+        for(int i = 0; i<n; i++) {
+            int pos = i, value = arr[i];
+            positions.push_back({value, pos});
+        }
+
+        std::sort(positions.begin(), positions.end());
+
+        std::vector<bool> visited(n, false);
+
+        int min_swaps = 0;
+        for(int i = 0; i<n; i++) {
+            if(visited[i] || positions[i].second == i) {
+                continue;
+            }
+
+            int cycle_size = 0, j = i;
+            while(!visited[j]) {
+                visited[j] = 1;
+                j = positions[j].second;
+                cycle_size++;
+            }
+
+            min_swaps += (cycle_size - 1);
+        }
+
+        return min_swaps;
+    };
+
+    std::map<int, int>  m;
+    for(int i = 0; i<n; i++) {
+        m[b[i]] = i;
+    }
+
+    for(int i = 0; i<n; i++) {
+        b[i] = m[a[i]];
+    }
+
+    return solve(b);
+}
+
+
+
+#endif

tests/algorithms/sorting/minimum_swaps.cc

@@ -0,0 +1,36 @@
+#include "../../../src/algorithms/sorting/minimum_swaps.h"
+#include "../../../third_party/catch.hpp"
+#include <random>
+#include <vector>
+#include <cstdlib>
+
+
+TEST_CASE("Testing minimum swaps [1]") {
+    std::vector<int> a {3, 6, 4, 8};
+    std::vector<int> b {4, 6, 8, 3};
+
+    REQUIRE(minimum_swaps(a, b) == 2);
+}
+
+TEST_CASE("Testing minimum swaps [2]") {
+    std::vector<int> a {1, 2, 3, 4};
+    std::vector<int> b {4, 3, 2, 1};
+
+    REQUIRE(minimum_swaps(a, b) == 2);
+}
+
+TEST_CASE("Testing minimum swaps [3]") {
+    std::vector<int> a {1, 2, 3, 4, 5, 6, 7};
+    std::vector<int> b {1, 2, 3, 4, 5, 6, 7};
+
+    REQUIRE(minimum_swaps(a, b) == 0);
+}
+
+TEST_CASE("Testing minimum swaps [4]") {
+    std::vector<int> a(100), b(100);
+    iota(a.begin(), a.end(), 1);
+    iota(b.begin(), b.end(), 1);
+
+    std::swap(a[0], a[99]);
+    REQUIRE(minimum_swaps(a, b) == 1);
+}