백준/ Silver 4 문제 , 백준 Node.js 자바스크립트 2491 , 수열

백준/ Silver 4 문제 , 백준 Node.js 자바스크립트 2491 , 수열

 

 

 

 

문제 출처

https://www.acmicpc.net/problem/2491

2491번: 수열

 

 

 

 

 

 

 

정답

 

 

1) 구현

 

const input = require("fs")
  .readFileSync("/dev/stdin")
  .toString()
  .trim()
  .split("\n");

const T = input[0];
const arr = input[1].split(" ").map(Number);

let Max_result = 0;
let Min_result = 0;
let Max_cnt = 1;
let Min_cnt = 1;
let check = true;

for (let i = 0; i < T - 1; i++) {
  if (i === 0) {
    if (arr[i] < arr[i + 1]) check = true;
    else if (arr[i] > arr[i + 1]) check = false;
  }
  if (arr[i] < arr[i + 1] && check === false) {
    check = true;
    if (Min_result < Min_cnt) {
      Min_result = Min_cnt;
    }
    Min_cnt = 1;
    Max_cnt += 1;
  } else if (arr[i] < arr[i + 1] && check === true) {
    Max_cnt += 1;
    Min_cnt = 1;
  } else if (arr[i] > arr[i + 1] && check === true) {
    check = false;
    if (Max_result < Max_cnt) {
      Max_result = Max_cnt;
    }
    Max_cnt = 1;
    Min_cnt += 1;
  } else if (arr[i] > arr[i + 1] && check === false) {
    Min_cnt += 1;
    Max_cnt = 1;
  } else {
    Max_cnt += 1;
    Min_cnt += 1;
  }
}
console.log(Math.max(Max_result, Min_result, Max_cnt, Min_cnt));

 

 

2) DP

 

 

 

const input = require("fs")
  .readFileSync("/dev/stdin")
  .toString()
  .trim()
  .split("\n");

const T = Number(input[0]);
const arr = input[1].split(" ").map(Number);

let up_arr = [...new Array(T)].fill(1);
let down_arr = [...new Array(T)].fill(1);
for (let i = 1; i < T; i++) {
  if (arr[i - 1] <= arr[i]) up_arr[i] = Math.max(up_arr[i], up_arr[i - 1] + 1);
  if (arr[i - 1] >= arr[i])
    down_arr[i] = Math.max(down_arr[i], down_arr[i - 1] + 1);
}
console.log(Math.max(Math.max(...up_arr), Math.max(...down_arr)));