[LeetCode] Perfect Squares

[LeetCode] Perfect Squares

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

For example, given n =12, Return3Because12 = 4 + 4 + 4; Given n =13, Return2Because13 = 4 + 9.

Credits:
Special thanks to @ jianchao. li. fighter for adding this problem and creating all test cases.

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Solutions

Dynamic Programming Method. Seasonal Initializationdp[i * i] = 1, The state transition equation isdp[i + j * j] = min(dp[i] + 1, dp[i + j * j]);

Implementation Code

C ++:

// Runtime: 544 msclass Solution {public:    int numSquares(int n) {        vector
  
    dp(n + 1, 0x7fffffff);        for (int i = 0; i * i <= n; i++)        {            dp[i * i] = 1;        }        for (int i = 1; i <= n; i++)        {            for (int j = 1; i + j * j <= n; j++)            {                dp[i + j * j] = min(dp[i] + 1, dp[i + j * j]);            }        }        return dp[n];    }};
  

Java:

// Runtime: 69 mspublic class Solution {    public int numSquares(int n) {        int dp[] = new int[n + 1];        Arrays.fill(dp, Integer.MAX_VALUE);        for (int i = 1; i * i <= n; i++) {            dp[i * i] = 1;        }        for (int i = 1; i <= n; i++) {            for (int j = 1; i + j * j <= n; j++) {                dp[i + j * j] = Math.min(dp[i] + 1, dp[i + j * j]);            }        }        return dp[n];    }}