前端——笔试

1.Linux创建用户并给每一个用户创建的默认目录是/bash
Linux强制结束进程的kill命令的参数是 kill -9 进程
2.canvas标签有width和height两个属性，style设置样式

• eg:<canvas id="canvas" width="500px" height="500px" style="border:1px solid blue"></canvas>

3.H5中用来获取当前位置的经纬度API是:navigator.geolocation.getCurrentPosition

https://blog.youkuaiyun.com/Jioho_chen/article/details/83592630?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522161639599516780357293600%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=161639599516780357293600&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduend~default-1-83592630.pc_search_result_no_baidu_js&utm_term=h5%E8%8E%B7%E5%8F%96%E5%BD%93%E5%89%8D%E4%BD%8D%E7%BD%AE%E7%BB%8F%E7%BA%AC%E5%BA%A6

4.MySQL中锁按粒度分类

• 表级锁
  • 表共享读锁
  • 表独占写锁
• 行级锁
  • 共享锁
  • 排它锁
• 页级锁

5.线程与进程

• https://blog.youkuaiyun.com/daaikuaichuan/article/details/82951084?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522161640411916780269899197%2522%252C%2522scm%2522%253A%252220140713.130102334…%2522%257D&request_id=161640411916780269899197&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2_allsobaiduend~default-1-82951084.pc_search_result_no_baidu_js&utm_term=%E8%BF%9B%E7%A8%8B%E4%B8%8E%E7%BA%BF%E7%A8%8B%E7%9A%84%E5%8C%BA%E5%88%AB%E4%B8%8E%E8%81%94%E7%B3%BB

6.资源间有序访问的实现是同步
7.求字符串子串是回文字符串的个数

• 暴力解决法

var countSubstrings = function(s) {
    var len = s.length;
    var left, right,maxArr = [],maxLength = 0;
    for(var i = 0; i < len; i++) {
        for(var j = i+1; j < len; j++) {
            left = i;
            right = j;
            var flag = false;
            maxLength = 0;
            while(left <= right) {
                flag = false;
                var m = left == right?1:2;
                if(s[left] == s[right]) {
                    maxLength += m;
                    flag = true;
                    left++;
                    right--;
                }else {
                    break;
                }
            }
            if(flag == true) {
                maxArr.push(maxLength);
            }
        }
    }
    return len + maxArr.length;//最长回文子串则是maxArr中最大值，需要先push(1)，可能是一个字符是最长回文子串
};

• 动态规划法

作者：xiao_ben_zhu
链接：https://leetcode-cn.com/problems/palindromic-substrings/solution/shou-hua-tu-jie-dong-tai-gui-hua-si-lu-by-hyj8/
来源：力扣（LeetCode）
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

const countSubstrings = (s) => {
  const len = s.length;
  let count = 0;
  const dp = new Array(len);
  for (let j = 0; j < len; j++) {
    for (let i = 0; i <= j; i++) {
      if (s[i] == s[j] && (j - i <= 1 || dp[i + 1])) {
        dp[i] = true;
        count++;
      } else {
        dp[i] = false;
      }
    }
  }
  return count;
};