每日算法刷题Day12-跳台阶、排列、替换空格、求n累加

5

8

#include<bits/stdc++.h>
using namespace std;

int n;
int ans = 0;

void foo( int k)
{
    if( k == n)ans++;
    else if(k < n)
    {
        foo(k+1);
        foo(k+2);
    }
}


int main()
{
    cin >>n;
    foo(0);
    cout << ans <<endl;
    return 0;
    
}

#include<bits/stdc++.h>
using namespace std;

int a[20];
int n;


int main()
{
    
    cin >>n;
    a[0] = 1;
    for( int i = 1; i <= n; i++)
    {
        a[i] = a[i-1] + a[i-2];
    }
    cout <<a[n];
    return 0;
    
}

3

1 2 3
1 3 2
2 1 3
2 3 1
3 1 2
3 2 1

#include<bits/stdc++.h>
using namespace std;

int N = 10;
int n;

void dfs(int u, int num[], bool st[])
{
    if(u > n)
    {
        for(int i = 1; i <= n; i++)cout << num[i]<< " ";
        cout << endl;
    }
    else 
    {
        for(int i = 1; i <= n; i++)
            if (!st[i])
            {
                st[i] = true;
                num[u] = i;
                dfs( u +1 , num ,st);
                st[i] = false;//恢复现场
            }
    }
}


int main()
{
    int num[N];
    bool st[N] = {0};//定义状态变量
    cin >> n;
    dfs(1,num,st);//从1开始排列
    return 0;
    
}

输入："We are happy."

输出："We%20are%20happy."

class Solution {
public:
    string replaceSpaces(string &str) {
        string res;
        for(auto c : str)
        {
            if(c == ' ')res += "%20";
            else res += c;
        }
        return res;
    }
};

输入：10

输出：55

class Solution {
public:
    int getSum(int n) {
        int sum = n;
        n > 0 && (sum += getSum(n - 1));
        return sum;
    }
};