feat: 双指针

26.remove-duplicates-from-sorted-array.java

@@ -0,0 +1,24 @@
+/*
+ * @lc app=leetcode id=26 lang=java
+ *
+ * [26] Remove Duplicates from Sorted Array
+ */
+
+// @lc code=start
+class Solution {
+    public int removeDuplicates(int[] nums) {
+        if(nums.length == 0) {
+            return 0;
+        }
+        int i = 0;
+        for(int j = 0; j< nums.length; j++) {
+            if(nums[j] != nums[i]) {
+                i++;
+                nums[i] = nums[j];
+            }
+        }
+        return i+1;
+    }
+}
+// @lc code=end
+

27.remove-element.java

@@ -0,0 +1,21 @@
+/*
+ * @lc app=leetcode id=27 lang=java
+ *
+ * [27] Remove Element
+ */
+
+// @lc code=start
+class Solution {
+    public int removeElement(int[] nums, int val) {
+        int i = 0;
+        for(int j = 0; j < nums.length; j++) {
+            if(nums[j] != val) {
+                nums[i] = nums[j];
+                i++;
+            }
+        }
+        return i;
+    }
+}
+// @lc code=end
+

28.find-the-index-of-the-first-occurrence-in-a-string.java

@@ -0,0 +1,24 @@
+/*
+ * @lc app=leetcode id=28 lang=java
+ *
+ * [28] Find the Index of the First Occurrence in a String
+ */
+
+// @lc code=start
+class Solution {
+    public int strStr(String haystack, String needle) {
+        int idx = -1;
+        if(haystack.length() < needle.length()) {
+            return idx;
+        }
+        for(int i = 0; i < haystack.length(); i++) {
+            if(i + needle.length() <= haystack.length() && haystack.substring(i, i + needle.length()).equals(needle))  {
+                idx = i;
+                break;
+            }
+        }
+        return idx;
+    }
+}
+// @lc code=end
+

80.remove-duplicates-from-sorted-array-ii.java

@@ -0,0 +1,26 @@
+/*
+ * @lc app=leetcode id=80 lang=java
+ *
+ * [80] Remove Duplicates from Sorted Array II
+ */
+
+// @lc code=start
+class Solution {
+    public int removeDuplicates(int[] nums) {
+        int i = -1, freq = 0;
+        for(int j = 0; j< nums.length; j++) {
+            if(i<0 || nums[i] == nums[j] && freq < 2) {
+                i++;
+                nums[i] = nums[j];
+                freq++;
+            } else if(nums[i] != nums[j]) {
+                freq = 1;
+                i++;
+                nums[i] = nums[j];
+            }
+        }
+        return i+1;
+    }
+}
+// @lc code=end
+