HDU 2064 汉诺塔III (递推)

题意：。。

析：dp[i] 表示把 i 个盘子搬到第 3 个柱子上最少步数，那么产生先把 i-1 个盘子搬到 第3个上，再把第 i 个搬到 第 2 个上，然后再把 i-1 个盘子，

从第3个柱子搬到第1个上，再把第 i 个盘子，搬到第3个上，再把第i-1个盘子从第1个柱子上搬到第3个上，所以总起来就是。

dp[i] = dp[i-1] * 3 + 2.

代码如下：

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>
#include <vector>
#include <map>
#include <cctype>
#include <cmath>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#define debug() puts("++++");
#define freopenr freopen("in.txt", "r", stdin)
#define freopenw freopen("out.txt", "w", stdout)
using namespace std;

typedef long long LL;
typedef pair<int, int> P;
const int INF = 0x3f3f3f3f;
const double inf = 0x3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int maxn = 40 + 5;
const int mod = 2000;
const int dr[] = {-1, 1, 0, 0};
const int dc[] = {0, 0, 1, -1};
const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};
int n, m;
const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
inline bool is_in(int r, int c){
    return r >= 0 && r < n && c >= 0 && c < m;
}
LL dp[maxn];

void init(){
    dp[1] = 2;
    for(int i = 2; i < 36; ++i)  dp[i] = dp[i-1] * 3LL + 2LL;
}

int main(){
    init();
    while(cin >> n)  cout << dp[n] << endl;
    return 0;
}