Today I have done leetcode's January LeetCoding Challenge with cpp.

January LeetCoding Challenge 15

Description

Jump Game IV

Given an array of integers arr, you are initially positioned at the first index of the array.

In one step you can jump from index i to index:

i + 1 where: i + 1 < arr.length.
i - 1 where: i - 1 >= 0.
j where: arr[i] == arr[j] and i != j.

Return the minimum number of steps to reach the last index of the array.

Notice that you can not jump outside of the array at any time.

Example 1:

Input: arr = [100,-23,-23,404,100,23,23,23,3,404]
Output: 3
Explanation: You need three jumps from index 0 --> 4 --> 3 --> 9. Note that index 9 is the last index of the array.

Example 2:

Input: arr = [7]
Output: 0
Explanation: Start index is the last index. You do not need to jump.

Example 3:

Input: arr = [7,6,9,6,9,6,9,7]
Output: 1
Explanation: You can jump directly from index 0 to index 7 which is last index of the array.

Constraints:

1 <= arr.length <= 5 * 10^4
-10^8 <= arr[i] <= 10^8

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
public:
  int minJumps(vector<int>& arr) {
    if(arr.size() < 3) return arr.size() - 1;
    unordered_map<int, vector<int>> positions;
    int len = arr.size();
    vector<bool> posVisit(len);
    for(int i = 0; i < len; ++i) {
      positions[arr[i]].push_back(i);
    }

    queue<pair<int, int>> q;
    q.push({0, 0});
    posVisit[0] = true;

    while(q.size()) {
      auto [cnt, pos] = q.front();
      if(pos == len - 1) return cnt;
      q.pop();
      if(pos && !posVisit[pos - 1]) {
        q.push({cnt + 1, pos - 1});
        posVisit[pos - 1] = true;
      }
      if(pos < len - 1 && !posVisit[pos + 1]) {
        q.push({cnt + 1, pos + 1});
        posVisit[pos + 1] = true;
      }
      int num = arr[pos];
      for(auto next : positions[num]) {
        if(next == pos) continue;
        posVisit[next] = true;
        q.push({cnt + 1, next});
      }
      positions[num].clear();
    }
    return - 1;
  }
};

// Accepted
// 32/32 cases passed (152 ms)
// Your runtime beats 90.78 % of cpp submissions
// Your memory usage beats 42.32 % of cpp submissions (70.8 MB)

2022-01-15 Daily-Challenge

January LeetCoding Challenge 15

Description

Solution