题目
约束
题解
解法一
class Solution {
public:
int climbStairs(int n) {
int p = 0, q = 0, r = 1;
for (int i = 1; i <= n; ++i) {
p = q;
q = r;
r = p + q;
}
return r;
}
};
解法二
class Solution {
public:
vector<vector<long long>> multiply(vector<vector<long long>> &a, vector<vector<long long>> &b) {
vector<vector<long long>> c(2, vector<long long>(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;
}
vector<vector<long long>> matrixPow(vector<vector<long long>> a, int n) {
vector<vector<long long>> ret = {{1, 0}, {0, 1}};
while (n > 0) {
if ((n & 1) == 1) {
ret = multiply(ret, a);
}
n >>= 1;
a = multiply(a, a);
}
return ret;
}
int climbStairs(int n) {
vector<vector<long long>> ret = {{1, 1}, {1, 0}};
vector<vector<long long>> res = matrixPow(ret, n);
return res[0][0];
}
};
解法三
class Solution {
public:
int climbStairs(int n) {
double sqrt5 = sqrt(5);
double fibn = pow((1 + sqrt5) / 2, n + 1) - pow((1 - sqrt5) / 2, n + 1);
return (int)round(fibn / sqrt5);
}
};
标签:爬楼梯,int,ret,vector,sqrt5,70,return,public,dp
From: https://www.cnblogs.com/chuixulvcao/p/17155702.html