fd

Author: dingjikerbo

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

@@ -61,14 +61,7 @@ public boolean containsNearbyAlmostDuplicate2(int[] nums, int k, int t) {
         Map<Long, Long> map = new HashMap<>();
 
         for (int i = 0; i < nums.length; i++) {
-            long index;
-
-            if (i >= k + 1) {
-                index = getBucketId(nums[i - k - 1], (long) t + 1);
-                map.remove(index);
-            }
-
-            index = getBucketId(nums[i], (long) t + 1);
+            long index = getBucketId(nums[i], (long) t + 1);
 
             if (map.containsKey(index)) {
                 return true;
@@ -83,6 +76,11 @@ public boolean containsNearbyAlmostDuplicate2(int[] nums, int k, int t) {
             }
 
             map.put(index, (long) nums[i]);
+
+            if (i >= k) {
+                index = getBucketId(nums[i - k], (long) t + 1);
+                map.remove(index);
+            }
         }
 
         return false;

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

@@ -11,28 +11,20 @@ public class IntersectionOfTwoArraysII {
 
     public int[] intersect(int[] nums1, int[] nums2) {
         HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
-        ArrayList<Integer> result = new ArrayList<Integer>();
-        for(int i = 0; i < nums1.length; i++)
-        {
-            if(map.containsKey(nums1[i])) map.put(nums1[i], map.get(nums1[i])+1);
-            else map.put(nums1[i], 1);
+        for (int i = 0; i < nums1.length; i++) {
+            map.put(nums1[i], map.getOrDefault(nums1[i], 0) + 1);
         }
-
-        for(int i = 0; i < nums2.length; i++)
-        {
-            if(map.containsKey(nums2[i]) && map.get(nums2[i]) > 0)
-            {
+        ArrayList<Integer> result = new ArrayList<Integer>();
+        for (int i = 0; i < nums2.length; i++) {
+            if (map.getOrDefault(nums2[i], 0) > 0) {
                 result.add(nums2[i]);
-                map.put(nums2[i], map.get(nums2[i])-1);
+                map.put(nums2[i], map.get(nums2[i]) - 1);
             }
         }
-
         int[] r = new int[result.size()];
-        for(int i = 0; i < result.size(); i++)
-        {
+        for (int i = 0; i < result.size(); i++) {
             r[i] = result.get(i);
         }
-
         return r;
     }
 }

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

@@ -8,16 +8,19 @@
 
 public class MaximumGap {
 
+    /**
+     * 这题核心是最大gap存在于跨桶的，而不是某个桶内部
+     * 首先刨去min和max，剩余n-2个数分散在n-1个桶中，必然导致有的桶里是空的
+     * 那么max gap必然是跨桶的
+     */
     // 耗时5ms，木桶原理
     public int maximumGap(int[] nums) {
         if (nums.length < 2) {
             return 0;
         }
 
         int min = Integer.MAX_VALUE, max = Integer.MIN_VALUE;
-        /**
-         * 首先找出数组中最大值和最小值
-         */
+
         for (int n : nums) {
             min = Math.min(min, n);
             max = Math.max(max, n);
@@ -27,32 +30,29 @@ public int maximumGap(int[] nums) {
             return 0;
         }
 
-        /**
-         * 有len个数，则有len-1个间隙，这里算出平均每个桶的宽度，桶的个数是len-1
-         */
-        int gap = (int) Math.ceil((double) (max - min) / (nums.length - 1));
-        int[] mins = new int[nums.length - 1], maxs = new int[nums.length - 1];
+        int bucketCount = nums.length - 1;
+        int gap = (int) Math.ceil((double) (max - min) / bucketCount);
+        int[] mins = new int[bucketCount], maxs = new int[bucketCount];
 
         Arrays.fill(mins, Integer.MAX_VALUE);
         Arrays.fill(maxs, Integer.MIN_VALUE);
 
         /**
-         * 这里要统计落在每个桶内的最大值和最小值
+         * 注意区间是左闭右开的，所以max没有包含进来，这里先去掉，最后再算
+         * 如果这里不略过max的话，算出来的index会越界
          */
         for (int n : nums) {
-            if (n == min || n == max) {
+            if (n == max) {
                 continue;
             }
-            /**
-             * 先算出n所在的桶
-             */
             int index = (n - min) / gap;
             mins[index] = Math.min(mins[index], n);
             maxs[index] = Math.max(maxs[index], n);
         }
 
-        int last = min, maxGap = Integer.MIN_VALUE;
-        for (int i = 0; i < nums.length - 1; i++) {
+        int last = min, maxGap = 0;
+        for (int i = 0; i < bucketCount; i++) {
+            // 略过空的桶
             if (mins[i] == Integer.MAX_VALUE) {
                 continue;
             }

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

@@ -27,6 +27,5 @@
 public class main {
 
     public static void main(String[] args) {
-
     }
 }