fd

Author: dingjikerbo

leetcode/solution/src/InsertDeleteGetRandom.java

@@ -10,43 +10,47 @@
 // 耗时111ms
 public class InsertDeleteGetRandom {
 
-    private HashMap<Integer, Integer> mMap;
-    private List<Integer> mList;
-    private Random mRandom;
+    ArrayList<Integer> list;
+    HashMap<Integer, Integer> map;
+    Random random;
 
+    /** Initialize your data structure here. */
     public InsertDeleteGetRandom() {
-        mList = new ArrayList<Integer>();
-        mMap = new HashMap<Integer, Integer>();
-        mRandom = new Random();
+        map = new HashMap<>();
+        list = new ArrayList<>();
+        random = new Random();
     }
 
+    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
     public boolean insert(int val) {
-        if (mMap.containsKey(val)) {
+        if (map.containsKey(val)) {
             return false;
         }
-        mList.add(val);
-        mMap.put(val, mList.size() - 1);
+        list.add(val);
+        map.put(val, list.size() - 1);
         return true;
     }
 
+    /** Removes a value from the set. Returns true if the set contained the specified element. */
     public boolean remove(int val) {
-        if (!mMap.containsKey(val)) {
+        int index = map.getOrDefault(val, -1);
+        if (index < 0) {
             return false;
         }
-        int index = mMap.remove(val);
-        int lastIndex = mList.size() - 1;
-        if (index != lastIndex) {
-            int lastVal = mList.get(lastIndex);
-            mList.set(index, lastVal);
-            // 这里要注意重新设置lastVal的index
-            mMap.put(lastVal, index);
+        if (index != list.size() - 1) {
+            int tail = list.get(list.size() - 1);
+            list.set(index, tail);
+            map.put(tail, index);
         }
-        mList.remove(lastIndex);
+        map.remove(val);
+        list.remove(list.size() - 1);
         return true;
     }
 
+    /** Get a random element from the set. */
     public int getRandom() {
-        int index = mRandom.nextInt(mList.size());
-        return mList.get(index);
+        int index = random.nextInt(list.size());
+        index = (index >= 0 ? index : -index);
+        return list.get(index);
     }
 }

leetcode/solution/src/ThreeSumClosest.java

@@ -5,30 +5,25 @@ public class ThreeSumClosest {
     public int threeSumClosest(int[] nums, int target) {
         Arrays.sort(nums);
 
-        long dis = Integer.MAX_VALUE, result = 0;
-
-        for (int i = 0; i < nums.length - 2; i++) {
-            int newTarget = target - nums[i];
-
-            for (int j = i + 1, k = nums.length - 1; j < k; ) {
-                int sum = nums[j] + nums[k];
-
-                if (sum > newTarget) {
-                    k--;
-                } else if (sum < newTarget) {
-                    j++;
+        int min = Integer.MAX_VALUE, res = 0;
+        for (int k = 0; k < nums.length - 2; k++) {
+
+            for (int i = k + 1, j = nums.length - 1; i < j; ) {
+                int sum = nums[k] + nums[i] + nums[j];
+                if (sum > target) {
+                    j--;
+                } else if (sum < target) {
+                    i++;
                 } else {
-                    return target;
+                    return sum;
                 }
-
-                long delta = Math.abs(newTarget - sum);
-                if (delta < dis) {
-                    dis = delta;
-                    result = sum + nums[i];
+                int delta = Math.abs(sum - target);
+                if (delta < min) {
+                    min = delta;
+                    res = sum;
                 }
             }
         }
-
-        return (int) result;
+        return res;
     }
 }

leetcode/src/Main.java

@@ -7,10 +7,54 @@ public static class Solution {
 
     }
 
+    class RandomizedSet {
+
+        ArrayList<Integer> list;
+        HashMap<Integer, Integer> map;
+        Random random;
+
+        /** Initialize your data structure here. */
+        public RandomizedSet() {
+            map = new HashMap<>();
+            list = new ArrayList<>();
+            random = new Random();
+        }
+
+        /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
+        public boolean insert(int val) {
+            if (map.containsKey(val)) {
+                return false;
+            }
+            list.add(val);
+            map.put(val, list.size() - 1);
+            return true;
+        }
+
+        /** Removes a value from the set. Returns true if the set contained the specified element. */
+        public boolean remove(int val) {
+            int index = map.getOrDefault(val, -1);
+            if (index < 0) {
+                return false;
+            }
+            if (index != list.size() - 1) {
+                int tail = list.get(list.size() - 1);
+                list.set(index, tail);
+                map.put(tail, index);
+            }
+            map.remove(val);
+            list.remove(list.size() - 1);
+            return true;
+        }
+
+        /** Get a random element from the set. */
+        public int getRandom() {
+            int index = random.nextInt() % list.size();
+            index = (index >= 0 ? index : -index);
+            return list.get(index);
+        }
+    }
 
     public static void main(String[] args) {
         Solution solution = new Solution();
-        String s = solution.mostCommonWord("Bob", new String[0]);
-        System.out.println(s);
     }
 }