2021-08-14 Daily-Challenge

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In: DailyChallenge
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Today is Saturday, I gonna review the tasks I've done this week, and finish today's leetcode's August LeetCoding Challenge with cpp.

LeetCode Review

Delete Leaves With a Given Value

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Minimum Number of Increments on Subarrays to Form a Target Array

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Minimum Falling Path Sum II

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Largest Time for Given Digits

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Set Matrix Zeroes

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Group Anagrams

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Array of Doubled Pairs

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Flip String to Monotone Increasing

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Add Strings

too easy to review

August LeetCoding Challenge 14

Description

Remove Boxes

You are given several boxes with different colors represented by different positive numbers.

You may experience several rounds to remove boxes until there is no box left. Each time you can choose some continuous boxes with the same color (i.e., composed of k boxes, k >= 1), remove them and get k * k points.

Return the maximum points you can get.

Example 1:

Input: boxes = [1,3,2,2,2,3,4,3,1]
Output: 23
Explanation:
[1, 3, 2, 2, 2, 3, 4, 3, 1] 
----> [1, 3, 3, 4, 3, 1] (3*3=9 points) 
----> [1, 3, 3, 3, 1] (1*1=1 points) 
----> [1, 1] (3*3=9 points) 
----> [] (2*2=4 points)

Example 2:

Input: boxes = [1,1,1]
Output: 9

Example 3:

Input: boxes = [1]
Output: 1

Constraints:

  • 1 <= boxes.length <= 100
  • 1 <= boxes[i] <= 100

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
struct Boxes {
  uint8_t color;
  uint8_t count;
};
const int N = 100;
uint16_t dp[N * N * N];
Boxes boxes[N];

class Solution {
  int n;
  uint16_t solve(uint8_t begin, uint8_t end, uint8_t cnt) {
    auto cache = dp + cnt * n * n + begin * n + end;
    if(*cache) return *cache;
    auto color = boxes[begin].color;
    if((end - begin) > 1 && boxes[end - 1].color == color) {
      cnt += boxes[end - 1].count;
      end -= 1;
    }
    cnt += boxes[begin].count;
    begin += 1;
    auto score = cnt * cnt;
    if(begin != end) {
      score += solve(begin, end, 0);
      for(auto mid = begin + 1; mid < end - 1; ++mid) {
        if(boxes[mid].color == color) {
          auto scoreRemove = solve(begin, mid, 0);
          auto scoreJoin = solve(mid, end, cnt);
          if(scoreRemove + scoreJoin > score) {
            score = scoreRemove + scoreJoin;
          }
        }
      }
    }
    // cout << int(begin) << ' ' << int(end) << ' ' << int(cnt) << ' ';
    // cout << score << endl;
    *cache = score;
    return score;
  }
public:
  int removeBoxes(vector<int>& boxesVec) {
    uint8_t pos = 0;
    uint8_t color = boxesVec.front();
    uint8_t count = 0;
    for(auto i : boxesVec) {
      if(i == color) {
        count += 1;
      } else {
        boxes[pos].count = count;
        boxes[pos].color = color;
        pos += 1;
        color = i;
        count = 1;
      }
    }
    boxes[pos].count = count;
    boxes[pos].color = color;
    n = pos + 1;
    if(n == 1) return boxes[0].count * boxes[0].count;
    memset(dp, 0, sizeof(uint16_t) * n * n * n);
    return solve(0, n, 0);
  }
};

// Accepted
// 62/62 cases passed (12 ms)
// Your runtime beats 96.3 % of cpp submissions
// Your memory usage beats 97.13 % of cpp submissions (9.7 MB)
Algorithm