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, return 3 because 12 = 4 + 4 + 4; given n = 13, return 2 because 13 = 4 + 9.

int numSquares(int n) {    if (n <= 1) return 1;        int logn = sqrt(n);    int *res = (int*)malloc((n + 1) * sizeof(int));    memset(res, 0, (n + 1) * sizeof(int));        for (int i = 0; i <= logn; ++i) res[i * i] = 1;        for (int i = 2; i <= n; ++i)    {        if (res[i] != 0) continue;                int tmp = res[i - 1] + 1;        int logi = sqrt(i);        for (int j = 2; j <= logi; ++j) {            if (tmp > res[i - j * j] + 1) tmp = res[i - j * j] + 1;        }        res[i] = tmp;    }        return res[n];}