力扣labuladong——一刷day04

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前言

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一、力扣26. 删除有序数组中的重复项

class Solution {
    public int removeDuplicates(int[] nums) {
        int i = 0, j = 0;
        for(; i < nums.length; ){
            if(nums[i] == nums[j]){
                i ++;
            }else{
                nums[++j] = nums[i++];
            }
        }
        return j + 1;
    }
}

二、力扣83. 删除排序链表中的重复元素

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if(head == null){
            return null;
        }
        ListNode p1 = head, p2 = head;
        while(p2 != null){
            if(p2.val == p1.val){
                p2 = p2.next;
            }else{
                p1 = p1.next;
                p1.val = p2.val;
                p2 = p2.next;
            }
        }
        p1.next = null;
        return head;
    }
}

三、力扣27. 移除元素

class Solution {
    public int removeElement(int[] nums, int val) {
        if(nums.length == 0){
            return 0;
        }
        int i = 0, j = 0;
        for(;i < nums.length; ){
            if(nums[i] != val){
                nums[j++] = nums[i++];
            }else{
                i ++;
            }
        }
        return j;
    }
}

四、力扣283. 移动零

class Solution {
    public void moveZeroes(int[] nums) {
        for(int i = 0,j = -1; i <nums.length; ){
            if(nums[i] != 0){
                int temp = nums[++j];
                nums[j] = nums[i];
                nums[i ++] = temp;
            }else{
                i ++;
            }
        }
    }
}

五、力扣167. 两数之和 II - 输入有序数组

class Solution {
    public int[] twoSum(int[] numbers, int target) {
        for(int i = 0, j = numbers.length-1; i < j;){
            if(numbers[i] + numbers[j] == target){
                return new int[]{i+1,j+1};
            }else if(numbers[i] + numbers[j] > target){
                j --;
            }else{
                i ++;
            }
        }
        return new int[2];
    }
}

六、力扣344. 反转字符串

class Solution {
    public void reverseString(char[] s) {
        for(int i = 0, j = s.length-1; i < j; i ++, j --){
            char temp = s[i];
            s[i] = s[j];
            s[j] = temp;
        }
    }
}

七、力扣5. 最长回文子串

class Solution {
    public String longestPalindrome(String s) {
        String res = "";
        for(int i = 0; i < s.length(); i ++){
            String s1 = fun(s,i,i);
            if(res.length() < s1.length()){
                res = s1;
            }
            if(i+1 < s.length()){
                String s2 = fun(s,i,i+1);
                if(res.length() < s2.length()){
                    res = s2;
                }
            }
        }
        return res;
    }
    public String fun(String s, int left, int right){
        while(left >= 0 && right < s.length()){
            if(s.charAt(left) != s.charAt(right)){
                return s.substring(left+1,right);
            }
            left --;
            right ++;
        }
        return s.substring(left+1,right);
    }
}