add 765

Author: fishercoder1534

src/main/java/com/fishercoder/solutions/_765.java

@@ -0,0 +1,60 @@
+package com.fishercoder.solutions;
+
+/**
+ * 765. Couples Holding Hands
+ *
+ * N couples sit in 2N seats arranged in a row and want to hold hands.
+ * We want to know the minimum number of swaps so that every couple is sitting side by side.
+ * A swap consists of choosing any two people, then they stand up and switch seats.
+ * The people and seats are represented by an integer from 0 to 2N-1, the couples are numbered in order,
+ * the first couple being (0, 1), the second couple being (2, 3), and so on with the last couple being (2N-2, 2N-1).
+ * The couples' initial seating is given by row[i] being the value of the person who is initially sitting in the i-th seat.
+
+ Example 1:
+
+ Input: row = [0, 2, 1, 3]
+ Output: 1
+ Explanation: We only need to swap the second (row[1]) and third (row[2]) person.
+
+ Example 2:
+
+ Input: row = [3, 2, 0, 1]
+ Output: 0
+ Explanation: All couples are already seated side by side.
+
+ Note:
+ len(row) is even and in the range of [4, 60].
+ row is guaranteed to be a permutation of 0...len(row)-1.
+ */
+
+public class _765 {
+  public static class Solution1 {
+    public int minSwapsCouples(int[] row) {
+      int swaps = 0;
+      for (int i = 0; i < row.length - 1; i += 2) {
+        int coupleValue = row[i] % 2 == 0 ? row[i] + 1 : row[i] - 1;
+        if (row[i + 1] != coupleValue) {
+          swaps++;
+          int coupleIndex = findIndex(row, coupleValue);
+          swap(row, coupleIndex, i + 1);
+        }
+      }
+      return swaps;
+    }
+
+    private void swap(int[] row, int i, int j) {
+      int tmp = row[i];
+      row[i] = row[j];
+      row[j] = tmp;
+    }
+
+    private int findIndex(int[] row, int value) {
+      for (int i = 0; i < row.length; i++) {
+        if (row[i] == value) {
+          return i;
+        }
+      }
+      return -1;
+    }
+  }
+}

src/test/java/com/fishercoder/_765Test.java

@@ -0,0 +1,41 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._765;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _765Test {
+  private static _765.Solution1 solution1;
+  private static int[] row;
+
+  @BeforeClass
+  public static void setup() {
+    solution1 = new _765.Solution1();
+  }
+
+  @Test
+  public void test1() {
+    row = new int[] {0, 2, 1, 3};
+    assertEquals(1, solution1.minSwapsCouples(row));
+  }
+
+  @Test
+  public void test2() {
+    row = new int[] {3, 2, 0, 1};
+    assertEquals(0, solution1.minSwapsCouples(row));
+  }
+
+  @Test
+  public void test3() {
+    row = new int[] {0, 4, 7, 3, 1, 5, 2, 8, 6, 9};
+    assertEquals(3, solution1.minSwapsCouples(row));
+  }
+
+  @Test
+  public void test4() {
+    row = new int[] {5, 6, 4, 0, 2, 1, 9, 3, 8, 7, 11, 10};
+    assertEquals(4, solution1.minSwapsCouples(row));
+  }
+}