day27

509 斐波拉契数

class Solution {
public:
int fib(int n) {
if(n <= 1)
{
return n;
}
vector dp(n+1);
dp[0] = 0;
dp[1] = 1;
for(int i = 2; i <= n; ++i)
{
dp[i] = dp[i - 1] + dp[i - 2];
}
return dp[n];
}
};

70 爬楼梯

class Solution {
public:
int climbStairs(int n) {
if(n <= 1)
{
return n;
}
vector dp(n+1);
dp[1] = 1;
dp[2] = 2;
for(int i = 3; i <= n; ++i)
{
dp[i] = dp[i-1] + dp[i-2];
}
return dp[n];
}
};

746 使用最小花费爬楼梯

class Solution {
public:
int minCostClimbingStairs(vector& cost) {
int n = cost.size();
vector dp(n+1);
dp[0] = 0;
dp[1] = 0;
for(int i = 2; i <= n; ++i)
{
dp[i] = min((dp[i-2] + cost[i-2]), (dp[i-1] + cost[i-1]));
}
return dp[n];
}
};