solve 75.sort-colors

Author: andavid

vscode/75.sort-colors.java

@@ -0,0 +1,68 @@
+/*
+ * @lc app=leetcode id=75 lang=java
+ *
+ * [75] Sort Colors
+ *
+ * https://leetcode.com/problems/sort-colors/description/
+ *
+ * algorithms
+ * Medium (43.01%)
+ * Likes:    1899
+ * Dislikes: 169
+ * Total Accepted:    349.2K
+ * Total Submissions: 810.9K
+ * Testcase Example:  '[2,0,2,1,1,0]'
+ *
+ * Given an array with n objects colored red, white or blue, sort them in-place
+ * so that objects of the same color are adjacent, with the colors in the order
+ * red, white and blue.
+ *
+ * Here, we will use the integers 0, 1, and 2 to represent the color red,
+ * white, and blue respectively.
+ *
+ * Note: You are not suppose to use the library's sort function for this
+ * problem.
+ *
+ * Example:
+ *
+ *
+ * Input: [2,0,2,1,1,0]
+ * Output: [0,0,1,1,2,2]
+ *
+ * Follow up:
+ *
+ *
+ * A rather straight forward solution is a two-pass algorithm using counting
+ * sort.
+ * First, iterate the array counting number of 0's, 1's, and 2's, then
+ * overwrite array with total number of 0's, then 1's and followed by 2's.
+ * Could you come up with a one-pass algorithm using only constant space?
+ *
+ *
+ */
+class Solution {
+  public void sortColors(int[] nums) {
+    Map<Integer, Integer> map = new HashMap<>();
+
+    for (int i = 0; i < nums.length; i++) {
+      if (map.containsKey(nums[i])) {
+        map.put(nums[i], map.get(nums[i]) + 1);
+      } else {
+        map.put(nums[i], 1);
+      }
+    }
+
+    int k = 0;
+    for (int key = 0; key <= 2; key++) {
+      int count = 0;
+      if (map.containsKey(key)) {
+        count = map.get(key);
+      }
+      while (count > 0) {
+        nums[k++] = key;
+        count--;
+      }
+    }
+  }
+}
+