Java | Leetcode Java题解之第509题斐波那契数

题目：

题解：

class Solution {public int fib(int n) {if (n < 2) {return n;}int[][] q = {{1, 1}, {1, 0}};int[][] res = pow(q, n - 1);return res[0][0];}public int[][] pow(int[][] a, int n) {int[][] ret = {{1, 0}, {0, 1}};while (n > 0) {if ((n & 1) == 1) {ret = multiply(ret, a);}n >>= 1;a = multiply(a, a);}return ret;}public int[][] multiply(int[][] a, int[][] b) {int[][] c = new int[2][2];for (int i = 0; i < 2; i++) {for (int j = 0; j < 2; j++) {c[i][j] = a[i][0] * b[0][j] + a[i][1] * b[1][j];}}return c;}
}