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

February LeetCoding Challenge 8

Description

Perfect Squares

Given an integer n, return the least number of perfect square numbers that sum to n.

A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, 1, 4, 9, and 16 are perfect squares while 3 and 11 are not.

Example 1:

Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.

Example 2:

Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

Constraints:

• 1 <= n <= 104

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
int answer[10001];
auto _ = [](){
  for(int i = 1; i < 10001; ++i) {
    answer[i] = INT_MAX;
    int bound = sqrt(i);
    for(int j = 1; j <= bound; ++j) {
      answer[i] = min(answer[i], answer[i - j * j] + 1);
    }
  }
  return 0;
}();
class Solution {
public:
  int numSquares(int n) {
    return answer[n];
  }
};

// Accepted
// 588/588 cases passed (4 ms)
// Your runtime beats 98.05 % of cpp submissions
// Your memory usage beats 95 % of cpp submissions (6 MB)