add 664

Author: fishercoder1534

README.md

@@ -22,6 +22,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|664|[Strange Printer](https://leetcode.com/problems/strange-printer/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_664.java) | O(n^3) | O(n^2) | Hard | DP
 |663|[Equal Tree Partition](https://leetcode.com/problems/equal-tree-partition/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_663.java) | O(n) | O(n) | Medium | Tree
 |662|[Maximum Width of Binary Tree](https://leetcode.com/problems/maximum-width-of-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_662.java) | O(n) | O(k) | Medium | BFS, DFS
 |661|[Image Smoother](https://leetcode.com/problems/image-smoother/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_661.java) | O(m*n) | O(1) | Easy | Array 

src/main/java/com/fishercoder/solutions/_664.java

@@ -0,0 +1,48 @@
+package com.fishercoder.solutions;
+
+/**
+ * 664. Strange Printer
+ *
+ * There is a strange printer with the following two special requirements:
+ * The printer can only print a sequence of the same character each time.
+ * At each turn, the printer can print new characters starting from and ending at any places, and will cover the original existing characters.
+ * Given a string consists of lower English letters only, your job is to count the minimum number of turns the printer needed in order to print it.
+
+ Example 1:
+ Input: "aaabbb"
+ Output: 2
+ Explanation: Print "aaa" first and then print "bbb".
+
+ Example 2:
+ Input: "aba"
+ Output: 2
+ Explanation: Print "aaa" first and then print "b" from the second place of the string, which will cover the existing character 'a'.
+
+ Hint: Length of the given string will not exceed 100.
+ */
+public class _664 {
+    /**reference: https://discuss.leetcode.com/topic/100137/java-solution-dp*/
+    public int strangePrinter(String s) {
+        int n = s.length();
+        if (n == 0) return 0;
+
+        int[][] dp = new int[101][101];
+        for (int i = 0; i < n; i++) {
+            dp[i][i] = 1;
+        }
+
+        for (int i = 1; i < n; i++) {
+            for (int j = 0; j < n - i; j++) {
+                dp[j][j + i] = i + 1;
+                for (int k = j + 1; k <= j + i; k++) {
+                    int temp = dp[j][k - 1] + dp[k][j + i];
+                    if (s.charAt(k - 1) == s.charAt(j + i)) {
+                        temp--;
+                    }
+                    dp[j][j + i] = Math.min(dp[j][j + i], temp);
+                }
+            }
+        }
+        return dp[0][n - 1];
+    }
+}

src/test/java/com/fishercoder/_664Test.java

@@ -0,0 +1,27 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._664;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _664Test {
+    private static _664 test;
+
+    @BeforeClass
+    public static void setup(){
+        test = new _664();
+    }
+
+    @Test
+    public void test1(){
+        assertEquals(2, test.strangePrinter("aaabbb"));
+    }
+
+    @Test
+    public void test2(){
+        assertEquals(2, test.strangePrinter("aba"));
+    }
+
+}