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Minimum number of squares whose sum equals to given number N | set 2
  • Difficulty Level : Hard
  • Last Updated : 15 Jun, 2021

A number can always be represented as a sum of squares of other numbers. Note that 1 is a square, and we can always break a number as (1*1 + 1*1 + 1*1 + …). Given a number N, the task is to represent N as the sum of minimum square numbers.

Examples:  

Input : 10 
Output : 1 + 9 
These are all possible ways 
1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 
1 + 1 + 1 + 1 + 1 + 1 + 4 
1 + 1 + 4 + 4 
1 + 9 
Choose one with minimum numbers

Input : 25 
Output : 25 

Prerequisites: Minimum number of squares whose sum equals to given number N
Approach: This is a typical application of dynamic programming. When we start from N = 6, we can reach 2 by subtracting the square of one i.e. one, 4 times, and by subtracting the square of two i.e. four, 1 time. So the subproblem for 2 is called twice. 
Since the same subproblems are called again, this problem has the Overlapping Subproblems property. So-min square sum problem has both properties (see this and this) of a dynamic programming problem. Like other typical Dynamic Programming(DP) problems, recomputation of the same subproblems can be avoided by constructing a temporary array table[][] in a bottom-up manner. 
Below is the implementation of the above approach: 



C++




// C++ program to represent N as the
// sum of minimum square numbers.
#include <bits/stdc++.h>
using namespace std;
 
// Function for finding
// minimum square numbers
vector<int> minSqrNum(int n)
{
  // A[i] of array arr store
  // minimum count of
  // square number to get i
  int arr[n + 1], k;
 
  // sqrNum[i] store last
  // square number to get i
  int sqrNum[n + 1];
  vector<int> v;
 
  // Initialize
  arr[0] = 0;
  sqrNum[0] = 0;
 
  // Find minimun count of
  // square number for
  // all value 1 to n
  for (int i = 1; i <= n; i++)
  {
    // In worst case it will
    // be arr[i-1]+1 we use all
    // combination of a[i-1] and add 1
    arr[i] = arr[i - 1] + 1;
    sqrNum[i] = 1;
 
    k = 1;
    // Check for all square
    // number less or equal to i
    while (k * k <= i)
    {
      // if it gives less
      // count then update it
      if (arr[i] > arr[i - k * k] + 1)
      {
        arr[i] = arr[i - k * k] + 1;
        sqrNum[i] = k * k;
      }
      k++;
    }
  }
 
  // Vector v stores optimum
  // square number whose sum give N
  while (n > 0)
  {
    v.push_back(sqrNum[n]);
    n -= sqrNum[n];
  }
  return v;
}
 
// Driver code
int main()
{
  int n = 10;
 
  vector<int> v;
 
  // Calling funcion
  v = minSqrNum(n);
 
  // Printing vector
  for (auto i = v.begin();
            i != v.end(); i++)
  {
    cout << *i;
    if (i + 1 != v.end())
      cout << " + ";
  }
  return 0;
}

Java




// Java program to represent
// N as the sum of minimum
// square numbers.
import java.util.*;
class GFG{
 
// Function for finding
// minimum square numbers
static Vector<Integer> minSqrNum(int n)
{
  // A[i] of array arr store
  // minimum count of
  // square number to get i
  int []arr = new int[n + 1];
  int k = 0;
 
  // sqrNum[i] store last
  // square number to get i
  int []sqrNum = new int[n + 1];
  Vector<Integer> v = new Vector<>();
 
  // Initialize
  arr[0] = 0;
  sqrNum[0] = 0;
 
  // Find minimun count of
  // square number for
  // all value 1 to n
  for (int i = 1; i <= n; i++)
  {
    // In worst case it will
    // be arr[i-1]+1 we use all
    // combination of a[i-1] and add 1
    arr[i] = arr[i - 1] + 1;
    sqrNum[i] = 1;
 
    k = 1;
    // Check for all square
    // number less or equal to i
    while (k * k <= i)
    {
      // if it gives less
      // count then update it
      if (arr[i] > arr[i - k * k] + 1)
      {
        arr[i] = arr[i - k * k] + 1;
        sqrNum[i] = k * k;
      }
      k++;
    }
  }
 
  // Vector v stores optimum
  // square number whose sum give N
  while (n > 0)
  {
    v.add(sqrNum[n]);
    n -= sqrNum[n];
  }
  return v;
}
 
// Driver code
public static void main(String[] args)
{
  int n = 10;
 
  Vector<Integer> v;
 
  // Calling funcion
  v = minSqrNum(n);
 
  // Printing vector
  for (int i = 0; i <v.size(); i++)
  {
    System.out.print(v.elementAt(i));
    if (i+1 != v.size())
      System.out.print(" + ");
  }
}
}
 
// This code is contributed by gauravrajput1

Python3




# Python3 program to represent N as the
# sum of minimum square numbers.
 
# Function for finding
# minimum square numbers
def minSqrNum(n):
 
    # arr[i] of array arr store
    # minimum count of
    # square number to get i
    arr = [0] * (n + 1)
     
    # sqrNum[i] store last
    # square number to get i
    sqrNum = [0] * (n + 1)
    v = []
 
    # Find minimun count of
    # square number for
    # all value 1 to n
    for i in range(n + 1):
         
        # In worst case it will
        # be arr[i-1]+1 we use all
        # combination of a[i-1] and add 1
        arr[i] = arr[i - 1] + 1
        sqrNum[i] = 1
 
        k = 1;
         
        # Check for all square
        # number less or equal to i
        while (k * k <= i):
             
            # If it gives less
            # count then update it
            if (arr[i] > arr[i - k * k] + 1):
                arr[i] = arr[i - k * k] + 1
                sqrNum[i] = k * k
 
            k += 1
 
    # v stores optimum
    # square number whose sum give N
    while (n > 0):
        v.append(sqrNum[n])
        n -= sqrNum[n];
         
    return v
 
# Driver code
n = 10
 
# Calling funcion
v = minSqrNum(n)
 
# Printing vector
for i in range(len(v)):
    print(v[i], end = "")
     
    if (i < len(v) - 1):
        print(" + ", end = "")
         
# This article is contributed by Apurvaraj

C#




// C# program to represent
// N as the sum of minimum
// square numbers.
using System;
using System.Collections.Generic;
class GFG{
 
// Function for finding
// minimum square numbers
static List<int> minSqrNum(int n)
{
  // A[i] of array arr store
  // minimum count of
  // square number to get i
  int []arr = new int[n + 1];
  int k = 0;
 
  // sqrNum[i] store last
  // square number to get i
  int []sqrNum = new int[n + 1];
  List<int> v = new List<int>();
 
  // Initialize
  arr[0] = 0;
  sqrNum[0] = 0;
 
  // Find minimun count of
  // square number for
  // all value 1 to n
  for (int i = 1; i <= n; i++)
  {
    // In worst case it will
    // be arr[i-1]+1 we use all
    // combination of a[i-1] and add 1
    arr[i] = arr[i - 1] + 1;
    sqrNum[i] = 1;
 
    k = 1;
    // Check for all square
    // number less or equal to i
    while (k * k <= i)
    {
      // if it gives less
      // count then update it
      if (arr[i] > arr[i - k * k] + 1)
      {
        arr[i] = arr[i - k * k] + 1;
        sqrNum[i] = k * k;
      }
      k++;
    }
  }
 
  // List v stores optimum
  // square number whose sum give N
  while (n > 0)
  {
    v.Add(sqrNum[n]);
    n -= sqrNum[n];
  }
  return v;
}
 
// Driver code
public static void Main(String[] args)
{
  int n = 10;
 
  List<int> v;
 
  // Calling funcion
  v = minSqrNum(n);
 
  // Printing vector
  for (int i = 0; i <v.Count; i++)
  {
    Console.Write(v[i]);
    if (i+1 != v.Count)
      Console.Write(" + ");
  }
}
}
 
// This code is contributed by gauravrajput1

Javascript




<script>
 
// Javascript program to represent N as the
// sum of minimum square numbers.
 
// Function for finding
// minimum square numbers
function minSqrNum(n)
{
  // A[i] of array arr store
  // minimum count of
  // square number to get i
  var arr = Array(n+1), k;
 
  // sqrNum[i] store last
  // square number to get i
  var sqrNum = Array(n+1);
  var v = [];
 
  // Initialize
  arr[0] = 0;
  sqrNum[0] = 0;
 
  // Find minimun count of
  // square number for
  // all value 1 to n
  for (var i = 1; i <= n; i++)
  {
    // In worst case it will
    // be arr[i-1]+1 we use all
    // combination of a[i-1] and add 1
    arr[i] = arr[i - 1] + 1;
    sqrNum[i] = 1;
 
    k = 1;
    // Check for all square
    // number less or equal to i
    while (k * k <= i)
    {
      // if it gives less
      // count then update it
      if (arr[i] > arr[i - k * k] + 1)
      {
        arr[i] = arr[i - k * k] + 1;
        sqrNum[i] = k * k;
      }
      k++;
    }
  }
 
  // Vector v stores optimum
  // square number whose sum give N
  while (n > 0)
  {
    v.push(sqrNum[n]);
    n -= sqrNum[n];
  }
  return v;
}
 
// Driver code
var n = 10;
var v = [];
// Calling funcion
v = minSqrNum(n);
// Printing vector
for(var i = 0; i<v.length; i++)
{
    document.write(v[i]);
  if (i + 1 != v.length)
    document.write( " + ");
}
 
 
</script>
Output: 
1 + 9

 

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