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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 ``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;``  ``sqrNum = 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 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 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 v;` `  ``// Calling funcion``  ``v = minSqrNum(n);` `  ``// Printing vector``  ``for` `(``int` `i = ``0``; i

## 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;``  ``sqrNum = 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

## Javascript

 ``
Output:
`1 + 9`

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