算法记录--好多内容也是借鉴大神的

1、链表翻转

/*
public class ListNode {
    int val;
    ListNode next = null;
 
    ListNode(int val) {
        this.val = val;
    }
}*/
 
public class Solution {
    public ListNode ReverseList(ListNode head) {
        // 记录上一个节点
        ListNode prev = null;
        // 记录当前节点
        ListNode curr = head;
        while (curr != null) {
            ListNode next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        return prev;
    }
}

2、二分查找

import java.util.*;
 
 
public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param nums int整型一维数组 
     * @param target int整型 
     * @return int整型
     */
    public int search (int[] nums, int target) {
        // write code here
        int left=0;
        int right=nums.length-1;
        while(left<=right){
            int mid=(right-left)/2+left;
            int num = nums[mid];
            if (num == target) {
                return mid;
            } else if (num > target) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return -1;
    }
}