Portfolio

쿠키 구입

문제

풀이

은찬


function solution(cookie) {
    const length = cookie.length;
    let answer = 0;
    
    for(let mid = 1; mid < length; mid++){
        let leftStart = mid - 1;
        let rightStart = mid;
        let leftSum = cookie[leftStart--];
        let rightSum = cookie[rightStart++];
        let keep = true;
        
        if(leftSum === rightSum){
            answer = Math.max(answer, rightSum);
        }
        
        while(keep){
            if(leftStart >= 0 && leftSum <= rightSum){
                leftSum += cookie[leftStart--];
            } else if(rightStart < length && rightSum <= leftSum){
                rightSum += cookie[rightStart++];
            } else{
                keep = false;
            }
            
            if(leftSum === rightSum){
                answer = Math.max(answer, rightSum);
            }
        }
    }
    
    return answer;
}

재영


// 구간합을 구하는 함수 생성
const getPrefixSum = (arr) => {
  const arrLength = arr.length;
  const arrPrefixSum = new Array(arrLength + 1).fill(0);

  for (let i = 0; i < arrLength; i += 1) {
    const now = arr[i];
    arrPrefixSum[i + 1] = now + arrPrefixSum[i];
  }
  return arrPrefixSum;
};

const solution = (cookie) => {
  if (cookie.length === 1) return 0;

  let result = 0;

  const cookiePrefixSum = getPrefixSum(cookie); // 착각 - 구간합을 구해줘야 한다는 생각
  const cookieLength = cookie.length;

  // 기준점 이동시키기
  for (let m = 0; m < cookieLength - 1; m += 1) {
    const leftEnd = m;
    const rightStart = m + 1;

    let leftStart = leftEnd;
    let rightEnd = rightStart;

    while (leftStart >= 0 && rightEnd < cookieLength) {
      let nowLeftSum = cookiePrefixSum[m + 1] - cookiePrefixSum[leftStart];
      let nowRightSum = cookiePrefixSum[rightEnd + 1] - cookiePrefixSum[m + 1];

      if (nowLeftSum === nowRightSum) {
        result = Math.max(nowLeftSum, result);

        rightEnd += 1;
        leftStart -= 1;
      } else if (nowLeftSum < nowRightSum) {
        leftStart -= 1;
      } else {
        rightEnd += 1;
      }
    }
  }

  return result;
};

효성


function solution(cookie) {
    if(cookie.length <= 1) {
        return 0;
    }
    
    const N = cookie.length;
    
    let maxCookie = 0;
    
    for(let m = 0; m < N - 1; m++) {
        let l = m, r = m + 1;
        let lSum = cookie[l], rSum = cookie[r];
        
        while(l >= 0 && r < N) {
            if(lSum === rSum) {
                maxCookie = Math.max(maxCookie, lSum);
                r++;
                l--;
                rSum += cookie[r];
                lSum += cookie[l];
            } else if(lSum > rSum && r + 1 < N) {
                r++;
                rSum += cookie[r];
            } else if(lSum < rSum && l - 1 >= 0) {
                l--;
                lSum += cookie[l];
            } else {
                break;
            }
        }
    }
    
    return maxCookie;
}