Leetcode Note: Perfect Squares

Leetcode Note: Perfect Squares

I. Description

Given a positive integer n, find the least number of perfect square numbers (for example,1, 4, 9, 16, ...) Which sumn.

For example, givenn = 12, Return 3 because12 = 4 + 4 + 4; Givenn = 13, Return 2 because13 = 4 + 9.

Ii. Question Analysis

The general idea of this question is to give a target integer and calculate the minimum number of the target integer from the total number of integers.

A better solution is to use dynamic planning. We all know the number of channels.xIt can be decomposed into an arbitrary number.aAdd a Worker Numberb * b, That isx = a + b * b. Therefore, it can constitute a target integer.xThe minimum number of workers is composedaAdd the minimum number of shards1.

Iii. Sample Code

class Solution {public:    int numSquares(int n) {        static vector
  
    sqrtNum(1, 0);        if(sqrtNum.size() >= n + 1)  return sqrtNum[n];        while(sqrtNum.size() <= n + 1){            int temp = INT_MAX;            for(int j = 1; j * j <= sqrtNum.size(); j++)                temp = min(temp, sqrtNum[sqrtNum.size() - j * j] + 1);            sqrtNum.push_back(temp);        }        return sqrtNum[n];    }};
  

Iv. Summary

Another use of dynamic planning. It is worth further learning!