摩尔投票

src/main/java/com/cdtft/leetcode/MinStack.java

@@ -0,0 +1,68 @@
+package com.cdtft.leetcode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * @author : wangcheng
+ * @date : 2020年05月11日 11:13
+ */
+public class MinStack {
+
+    private Integer minValue;
+
+    private List<Node> nodeList;
+
+    public MinStack() {
+        this.nodeList = new ArrayList<>();
+    }
+
+    public void push(int x) {
+        if (nodeList.size() == 0) {
+            minValue = x;
+        }
+
+        nodeList.add(new Node(x - minValue, x));
+        if (x  < minValue) {
+            minValue = x;
+        }
+    }
+
+    public void pop() {
+        if (nodeList.size() == 0) {
+            return;
+        }
+        Node node = nodeList.remove(nodeList.size() - 1);
+        if (node.diff < 0) {
+            refreshMinValue(node);
+        }
+    }
+
+    public int top() {
+        if (nodeList.size() == 0) {
+            return Integer.MAX_VALUE;
+        }
+        Node node = nodeList.get(nodeList.size() - 1);
+        return node.value;
+    }
+
+    public int getMin() {
+        return minValue;
+    }
+
+    private void refreshMinValue(Node node) {
+        minValue = node.value - node.diff;
+    }
+
+    private class Node {
+
+        Integer diff;
+
+        Integer value;
+
+        public Node(Integer diff, Integer value) {
+            this.diff = diff;
+            this.value = value;
+        }
+    }
+}

src/main/java/com/cdtft/leetcode/Solution.java

@@ -1,8 +1,10 @@
 package com.cdtft.leetcode;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Map;
 import java.util.Stack;
 import java.util.TreeMap;
@@ -379,6 +381,38 @@ public boolean isPalindrome(String s) {
         return true;
     }
 
+    public int singleNumber(int[] nums) {
+        int result = 0;
+        for (int i : nums) {
+            result ^= nums[i];
+        }
+        return result;
+    }
+
+    public int majorityElement(int[] nums) {
+        Arrays.sort(nums);
+        return nums[nums.length / 2];
+    }
+
+    /**
+     * 摩尔投票
+     *
+     * @param nums
+     * @return
+     */
+    public int majorityElement_1(int[] nums) {
+        int cand = nums[0];
+        int count = 1;
+        for (int i = 1; i < nums.length - 1; i++) {
+            if (cand == nums[i]) {
+                count++;
+            } else if (--count == 0) {
+                cand = nums[i];
+                cand = 1;
+            }
+        }
+        return cand;
+    }
 
     public static void main(String[] args) {
         LinkedList<Integer> list = new LinkedList<>();

src/test/java/com/cdtft/leetcode/MinStackTest.java

@@ -0,0 +1,35 @@
+package com.cdtft.leetcode;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * ["MinStack","push","push","push","top","pop","getMin","pop","getMin","pop","push","top","getMin","push","top",
+ * "getMin","pop","getMin"]
+ * [[],[2147483646],[2147483646],[2147483647],[],[],[],[],[],[],[2147483647],[],[],[-2147483648],[],[],[],[]]
+ */
+public class MinStackTest {
+
+    @Test
+    public void push() {
+        MinStack minStack = new MinStack();
+        minStack.push(2147483646);
+        minStack.push(2147483646);
+        minStack.push(2147483647);
+        System.out.println(minStack.top());
+        minStack.pop();
+        System.out.println(minStack.getMin());
+        minStack.pop();
+        System.out.println(minStack.getMin());
+        minStack.pop();
+        minStack.push(2147483647);
+        System.out.println(minStack.top());
+        System.out.println(minStack.getMin());
+        minStack.push(-2147483648);
+        System.out.println(minStack.top());
+        System.out.println(minStack.getMin());
+        minStack.pop();
+        System.out.println(minStack.getMin());
+    }
+}

src/test/java/com/cdtft/leetcode/SolutionTest.java

@@ -103,4 +103,10 @@ public void maxProfit() {
     public void isPalindrome() {
         System.out.println(solution.isPalindrome("race a car"));
     }
+
+    @Test
+    public void singleNumber() {
+        int[] nums = new int[]{2, 2, 1};
+        System.out.println(2^2^2);
+    }
 }