Share my backtracking solution


  • 1
    N
    public class Solution {
        public int numSquares(int n) {
            int init = (int)Math.sqrt(n);
            search(n, 0, 0, init);
            return min;
        }
        
        private int min = Integer.MAX_VALUE;
        
        private void search(int target, int sum, int depth, int n) {
            // if the least number of perfect square numbers is greater than the min value, we don't need to go deeper
            if (depth > min) return;
            
            if (target == sum) {
                min = Math.min(min, depth);
                return;
            } else if (target < sum) return;
            
            for (; n > 0; n--) {
                int temp = n * n;
                sum += temp;
                
                search(target, sum, depth + 1, n);
                
                sum -= temp;
            }
        }
    }
    
    

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