add 581

fishercoder1534 · fishercoder1534 · commit d70d09b90e49 · 2017-05-17T08:22:55.000-07:00
diff --git a/README.md b/README.md
@@ -20,6 +20,7 @@ Your ideas/fixes/algorithms are more than welcome!
 
 |  #  |      Title     |   Solutions   | Time          | Space         | Difficulty  | Tag          | Notes
 |-----|----------------|---------------|---------------|---------------|-------------|--------------|-----
+|581|[Shortest Unsorted Continuous Subarray](https://leetcode.com/problems/shortest-unsorted-continuous-subarray/)|[Solution](../master/src/main/java/com/stevesun/solutions/_581.java) | O(n) |O(1) | Easy | Array, Sort
 |575|[Distribute Candies](https://leetcode.com/problems/distribute-candies/)|[Solution](../master/src/main/java/com/stevesun/solutions/_575.java) | O(nlogn) |O(1) | Easy | Array
 |572|[Subtree of Another Tree](https://leetcode.com/problems/subtree-of-another-tree/)|[Solution](../master/src/main/java/com/stevesun/solutions/_572.java) | O(m*n) |O(1) | Easy | Tree
 |567|[Permutation in String](https://leetcode.com/problems/permutation-in-string/)|[Solution](../master/src/main/java/com/stevesun/solutions/_567.java) | O(max(m,n)) |O(1) | Medium | Sliding Windows, Two Pointers
diff --git a/src/main/java/com/stevesun/solutions/_581.java b/src/main/java/com/stevesun/solutions/_581.java
@@ -0,0 +1,57 @@
+package com.stevesun.solutions;
+
+import java.util.Arrays;
+
+/**
+ * 581. Shortest Unsorted Continuous Subarray
+ *
+ * Given an integer array, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order, too.
+
+ You need to find the shortest such subarray and output its length.
+
+ Example 1:
+ Input: [2, 6, 4, 8, 10, 9, 15]
+ Output: 5
+ Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.
+
+ Note:
+ Then length of the input array is in range [1, 10,000].
+ The input array may contain duplicates, so ascending order here means <=.
+
+ */
+public class _581 {
+
+    /**credit: https://discuss.leetcode.com/topic/89282/java-o-n-time-o-1-space
+     * Use start and end to keep track of the minimum subarray nums[start...end] which must be sorted for the entire array nums.
+     * If start < end < 0 at the end of the for loop, then the array is already fully sorted.
+     *
+     * Time: O(n)
+     * Space: O(1)*/
+    public int findUnsortedSubarray(int[] nums) {
+        int n = nums.length, start = -1, end = -2, min = nums[n-1], max = nums[0];
+        for (int i=1;i<n;i++) {
+            max = Math.max(max, nums[i]);
+            min = Math.min(min, nums[n-1-i]);
+            if (nums[i] < max) end = i;
+            if (nums[n-1-i] > min) start = n-1-i;
+        }
+        return end - start + 1;
+    }
+
+    /**Time: O(nlogn)
+     * Space: O(n)*/
+    public int findUnsortedSubarray_sorting(int[] nums) {
+        int[] clones = nums.clone();
+        Arrays.sort(clones);
+        int start = nums.length;
+        int end = 0;
+        for (int i = 0; i < nums.length; i++) {
+            if (clones[i] != nums[i]) {
+                start = Math.min(start, i);
+                end = Math.max(end, i);
+            }
+        }
+        return (end - start > 0) ? end-start+1 : 0;
+    }
+
+}
diff --git a/src/test/java/com/stevesun/_581Test.java b/src/test/java/com/stevesun/_581Test.java
@@ -0,0 +1,34 @@
+package com.stevesun;
+
+import com.stevesun.solutions._48;
+import com.stevesun.solutions._581;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Created by stevesun on 5/17/17.
+ */
+public class _581Test {
+    private static _581 test;
+    private static int[] nums;
+
+    @BeforeClass
+    public static void setup(){
+        test = new _581();
+    }
+
+    @Test
+    public void test1(){
+        nums = new int[]{1,2,3,4};
+        assertEquals(0, test.findUnsortedSubarray(nums));
+        assertEquals(0, test.findUnsortedSubarray_sorting(nums));
+    }
+
+    @Test
+    public void test2(){
+        nums = new int[]{2,6,4,8,10,9,15};
+        assertEquals(5, test.findUnsortedSubarray(nums));
+    }
+}
