Given an integer n, return the least number of perfect square numbers that sum ton.
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.
Constraints
1 <= n <= 104
Approach
Links
Binarysearch
GeeksforGeeks
ProgramCreek
YouTube
Examples
Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.
Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.
Solutions
/**
* Time complexity :
* Space complexity :
*/
class Solution {
public int numSquares(int n) {
if(n < 1) {
return 0;
}
int noOfSquares = (int)Math.sqrt(n) + 1;
int[] squareNumbers = new int[noOfSquares];
for(int i = 1; i < noOfSquares; i++) {
squareNumbers[i] = i*i;
}
int[] dp = new int[n+1];
Arrays.fill(dp, Integer.MAX_VALUE);
dp[0] = 0;
for(int i = 1; i <= n; i++) {
for(int s = 1; s < noOfSquares; s++) {
int squareNumber = squareNumbers[s];
if(i < squareNumber) {
break;
}
dp[i] = Math.min(dp[i], dp[i-squareNumber]+1);
}
}
return dp[n];
}
}