70.Climbing Stairs
作者:互联网
递归解决方法
public class Main {
int sum = 0;
public int climbStairs(int n) {
if (n <= 0) {//
sum++;
} else if (n == 1) {
sum++;
} else {
climbStairs(n - 1);//每一种结果都有两种选择 要么一步 要么两步
climbStairs(n - 2);
}
return sum;
}
public static void main(String[]args) {
Main m=new Main();
System.out.println(m.climbStairs(2));
}
}
非递归
public class Main {
int sum = 0;
public int climbStairs(int n) {
if (n <= 1) {
return 1;
} else {
int[] arr = new int[n];
arr[0] = 1;
arr[1] = 2;
int i = 2;
while (i < n && i>= 2) {
arr[i ] = arr[i-1] + arr[i - 2];//每一个都是前两位之和
i++;
}
return arr[n - 1];
}
}
public static void main(String[] args) {
Main m = new Main();
System.out.println(m.climbStairs(8));
}
}
其他人解法也是大同小异
private int[] memo;
public int climbStairs(int n) {
memo = new int[n + 1];
Arrays.fill(memo, -1);
return getClimbStairs(n);
}
private int getClimbStairs(int n) {
if (n == 1) {
return 1;
}
if (n == 2) {
return 2;
}
if (memo[n] == -1) {
memo[n] = getClimbStairs(n - 1) + getClimbStairs(n - 2);
}
return memo[n];
}
}
int climbStairs(int n){
int x1=0,x2=1;
int i;
int sum;
for(i=1;i<=n;i++)
{
sum=x1+x2;
x1=x2;
x2=sum;
}
return sum;
}
哈希表 有趣
public class Solution {
int result;
HashMap<Integer, Integer> memo = new HashMap<Integer, Integer>();
public int climbStairs(int n) {
if(n < 2) {
return 1;
}
if(memo.containsKey(n)) {
return memo.get(n);
}
result = climbStairs(n-1) + climbStairs(n-2);
memo.put(n,result);
return result;
}
}
标签:arr,return,int,memo,climbStairs,70,Climbing,Stairs,public 来源: https://www.cnblogs.com/cznczai/p/11150521.html