fd

Author: dingjikerbo

README.md

@@ -369,6 +369,7 @@
 |535|[Encode and Decode TinyURL](https://leetcode.com/problems/encode-and-decode-tinyurl/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/EncodeAndDecodeTinyURL.java)|100||
 |541|[Reverse String II](https://leetcode.com/problems/reverse-string-ii/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/ReverseStringII.java)|100||
 |557|[Reverse Words in a String III](https://leetcode.com/problems/reverse-words-in-a-string-iii/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/ReverseWordsInAStringIII.java)|100||
+|560|[Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/SubarraySumEqualsK.java)|70||
 |637|[Average of Levels in Binary Tree](https://leetcode.com/problems/average-of-levels-in-binary-tree/#/description)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/AverageOfLevelsInBinaryTree.java)|100||
 |652|[Find Duplicate Subtrees](https://leetcode.com/problems/find-duplicate-subtrees/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/FindDuplicateSubtrees.java)|70|开始还没思路|
 |653|[Two Sum IV - Input is a BST](https://leetcode.com/problems/two-sum-iv-input-is-a-bst/)| [Java](https://github.com/dingjikerbo/leetcode/blob/master/solution/src/main/java/com/inuker/solution/TwoSumIV.java)|90||

solution/src/main/java/com/inuker/solution/SubarraySumEqualsK.java

@@ -0,0 +1,26 @@
+package com.inuker.solution;
+
+import java.util.HashMap;
+
+/**
+ * Created by liwentian on 2017/12/5.
+ * https://leetcode.com/articles/subarray-sum-equals-k/
+ */
+
+public class SubarraySumEqualsK {
+
+    /**
+     * 注意map.put(0,1)，即当前数自己也算是一种
+     */
+    public int subarraySum(int[] nums, int k) {
+        HashMap<Integer, Integer> map = new HashMap<>();
+        map.put(0, 1);
+        int count = 0;
+        for (int i = 0, sum = 0; i < nums.length; i++) {
+            sum += nums[i];
+            count += map.getOrDefault(sum - k, 0);
+            map.put(sum, map.getOrDefault(sum, 0) + 1);
+        }
+        return count;
+    }
+}

test/src/main/java/com/inuker/test/Test2.java

@@ -1,6 +1,7 @@
 package com.inuker.test;
 
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -10,72 +11,15 @@
 
 public class Test2 {
 
-    public double[] medianSlidingWindow(int[] nums, int k) {
-        MyMap up = new MyMap();
-        MyMap down = new MyMap(Comparator.reverseOrder());
-        double[] result = new double[nums.length - k + 1];
-        for (int i = 0; i < nums.length; i++) {
-            up.myAdd(nums[i]);
-            down.myAdd(up.myPollFirst());
-
-            if (i >= k) {
-                if (up.containsKey(nums[i - k])) {
-                    up.myRemove(nums[i - k]);
-                } else {
-                    down.myRemove(nums[i - k]);
-                }
-            }
-
-            if (up.size < down.size) {
-                up.myAdd(down.myPollFirst());
-            }
-            if (i >= k - 1) {
-                result[i - k + 1] = up.size == down.size
-                        ? ((double) up.firstKey() + down.firstKey()) / 2 : up.firstKey();
-            }
-        }
-        return result;
-    }
-
-    class MyMap extends TreeMap<Integer, Integer> {
-        int size;
-
-        MyMap() {
-            super();
-        }
-
-        MyMap(Comparator<Integer> comparator) {
-            super(comparator);
-        }
-
-        void myAdd(int n) {
-            put(n, getOrDefault(n, 0) + 1);
-            size++;
-        }
-
-        boolean myRemove(int n) {
-            int count = getOrDefault(n, 0);
-            if (count == 0) {
-                return false;
-            }
-            if (count == 1) {
-                remove(n);
-            } else {
-                put(n, count - 1);
-            }
-            size--;
-            return true;
-        }
-
-        int myPollFirst() {
-            Map.Entry<Integer, Integer> entry = firstEntry();
-            if (entry.getValue() == 1) {
-                pollFirstEntry();
-            } else {
-                put(entry.getKey(), entry.getValue() - 1);
-            }
-            size--;
-            return entry.getKey();
+    public int subarraySum(int[] nums, int k) {
+        HashMap<Integer, Integer> map = new HashMap<>();
+        map.put(0, 1);
+        int count = 0;
+        for (int i = 0, sum = 0; i < nums.length; i++) {
+            sum += nums[i];
+            count += map.getOrDefault(sum - k, 0);
+            map.put(sum, map.getOrDefault(sum, 0) + 1);
         }
+        return count;
     }
 }

test/src/main/java/com/inuker/test/main.java

@@ -27,11 +27,5 @@
 public class main {
 
     public static void main(String[] args) {
-        double[] f = new Test2().medianSlidingWindow(new int[] {
-                Integer.MAX_VALUE, 1, 2, 3, 4, 5, 6, 7, Integer.MAX_VALUE
-        }, 2);
-        for (double d : f) {
-            System.out.print(d + " ");
-        }
     }
 }