前端动态规划

没办法了，动态规划绕不过去了，那就搞懂吧。

HJ24 合唱队 - 中等

var num;
while(num = parseInt(readline())){
    const arr = readline().split(' ').slice(0,num).map(n => parseInt(n));
    let dp1 = handle(arr);
    let dp2 = handle(arr.reverse()).reverse();
    let max = 0;
    for (let i = 0; i<dp1.length; i++){
        max = Math.max(max, dp1[i]+dp2[i]-1);
    }
    console.log(arr.length - max);
}

function handle(arr) {
    const dp = [];
    for (let i = 0; i<arr.length; i++) {
        dp[i] = 1;
        for (let j = 0; j <i; j++) {
            if (arr[j] < arr[i]) {
                dp[i] = Math.max(dp[i], dp[j]+1);
            }
        } 
    }
    return dp;
}

　　

HJ32 密码截取 - 简单，可以有其他方法

const line = readline();

const dp = [];
let max = 0;

for (let i = 0; i < line.length; i++){
    dp[i] = 1;
    for (let j = 0; j <=i; j++){
        let str = line.slice(j, i+1);
        if (check(str)) {
            dp[i] = Math.max(dp[i], str.length);
            max = Math.max(max, dp[i]);
        }
        
    }
}

console.log(max)

function check(str) {
    let i,j;
    if (str.length %2 ===0) {
        i = str.length/2-1;
        j = str.length/2;
    } else {
        i = (str.length-1)/2;
        j = i;
    }
    while (i >=0 && j<str.length) {
            if (str[i] === str[j]) {
                i--;j++
            } else {
                return false;
            }
        }
        return true;
}

　　HJ75 公共子串计算 - 简单，可以有其他方法

const line = readline();
const line2 = readline();

let short, long;
if (line.length >= line2.length) {
    short = line2;
    long = line;
} else {
    short = line;
    long = line2;
}

let dp = [];
let max = 0;

for (let i = 0; i < short.length; i++){
    dp[i] = 0;
    for (let j = 0; j <= i; j++) {
        let str = short.slice(j,i+1);
        if (long.indexOf(str) > -1) {
            dp[i] = Math.max(str.length, dp[i]);
            max = Math.max(max, dp[i])
        }
    }
}

console.log(max);

　　HJ52 计算字符串的编辑距离 - 难