更新 Solution.java

src/solution/Solution.java

@@ -1,6 +1,8 @@
 package solution;
 
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Set;
 
 public class Solution {
@@ -25,4 +27,56 @@ public class Solution {
         }
         return ans;
     }
+    //计算最大价格
+    public static int maxProfit(int[] prices) {
+        if (prices == null || prices.length == 0) {
+            return 0;
+        }
+
+        int minPrice = prices[0];
+        int maxProfit = 0;
+
+        for (int price : prices) {
+            // 更新最小价格
+            minPrice = Math.min(minPrice, price);
+
+            // 计算当前价格的潜在利润并更新最大利润
+            int potentialProfit = price - minPrice;
+            maxProfit = Math.max(maxProfit, potentialProfit);
+        }
+
+        return maxProfit;
+    }
+
+
+    //哈希映射算法（Hash Mapping Algorithm）用于找出一个数组中的众数（majority element）
+    public int majorityElement(int[] nums) {
+        Map<Integer, Integer> map = new HashMap<>();
+        // maxNum 表示元素，maxCount 表示元素出现的次数
+        int maxNum = 0, maxCount = 0;
+        for (int num: nums) {
+            int count = map.getOrDefault(num, 0) + 1;
+            map.put(num, count);
+            if (count > maxCount) {
+                maxCount = count;
+                maxNum = num;
+            }
+        }
+        return maxNum;
+    }
+    //摩尔投票算法（Boyer-Moore Voting Algorithm）来找出数组中的众数
+    public static int majorityElement1(int[] nums) {
+        int candidate = nums[0], count = 1;
+        for (int i = 1; i < nums.length; ++i) {
+            if (count == 0) {
+                candidate = nums[i];
+                count = 1;
+            } else if (nums[i] == candidate) {
+                count++;
+            } else{
+                count--;
+            }
+        }
+        return candidate;
+    }
 }