题解 | #密码截取#

const readline = require('readline');

const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
});
rl.on('line', function (line) {
    let max = 1
  for (let i = 0 ; i < line.length; i++){
    let temp1 = findMax(line,i, i)
    let temp2 = line.charAt(i)===line.charAt(i+1)?findMax(line, i, i+1):1
    max = Math.max(max, temp1, temp2)
  }
  console.log(max)
});

function findMax(str:string, left:number, right: number){
    let max = 1 
    while (left >= 0 && right < str.length){
        
        if (str.charAt(left)===str.charAt(right)){
            max = Math.max(max, right-left+1)
            left -= 1 
              right += 1
        }else{
            break
        }
      
    }

    return max
}

双指针。

一个字符串是不是回文串如何判断。

单个字符串必然是回文串，之后向两边扩散就好