UVa 1374

本题值得学习的地方就是乐观估计函数的推到，需要数学指数的运算，另外计算2的n次方的时候可以用1<<n来快速计算，值得学习。

另外对于当前的集合存储，用C数列存储再合适不过了，刚开始用set来存，对数据进行增删浪费了大量时间，而且操作起来特别麻烦。

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

int n, maxd, res[32];

bool DFS(int d)
{
    if(d == maxd) return res[d-1]==n;
    if(*max_element(res, res+d) * (1<<(maxd-d)) < n) return false;
    for(int i = d-1; i >= 0; --i){
        int v1 = res[d-1] + res[i], v2 = abs(res[d-1] - res[i]);
        if(!count(res, res+d, v1)){
            res[d] = v1;
            if(DFS(d+1)) return true;
        }
        if(!count(res, res+d, v2)){
            res[d] = v2;
            if(DFS(d+1)) return true;
        }
    }
    return false;
}

int main()
{
    while(res[0] = 1, maxd = 1, scanf("%d", &n), n){
        while(!DFS(1))
            maxd++;
        printf("%d
", maxd - 1);
    }
	return 0;
}

打表的方法，只用了9ms

#include <stdio.h>
int res[1024] = {0, 0, 1, 2, 2, 3, 3, 4, 3, 4, 4, 5, 4, 5, 5, 5, 4, 5, 5, 6, 5, 6, 6, 6, 5, 6, 6, 6, 6, 7, 6, 6, 5, 6, 6, 7, 6, 7, 7, 7, 6, 7, 7, 7, 7, 7, 7, 7, 6, 7, 7, 7, 7, 8, 7, 8, 7, 8, 8, 8, 7, 8, 7, 7, 6, 7, 7, 8, 7, 8, 8, 8, 7, 8, 8, 8, 8, 8, 8, 8, 7, 8, 8, 8, 8, 8, 8, 9, 8, 9, 8, 9, 8, 8, 8, 8, 7, 8, 8, 8, 8, 9, 8, 9, 8, 9, 9, 9, 8, 9, 9, 9, 8, 9, 9, 9, 9, 9, 9, 9, 8, 9, 9, 9, 8, 9, 8, 8, 7, 8, 8, 9, 8, 9, 9, 9, 8, 9, 9, 9, 9, 9, 9, 9, 8, 9, 9, 9, 9, 9, 9, 10, 9, 9, 9, 9, 9, 9, 9, 9, 8, 9, 9, 9, 9, 9, 9, 10, 9, 10, 9, 10, 9, 10, 10, 10, 9, 10, 10, 10, 9, 10, 10, 10, 9, 10, 9, 10, 9, 9, 9, 9, 8, 9, 9, 9, 9, 10, 9, 10, 9, 10, 10, 10, 9, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 9, 10, 9, 9, 8, 9, 9, 10, 9, 10, 10, 10, 9, 10, 10, 11, 10, 11, 10, 10, 9, 10, 10, 11, 10, 11, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 11, 10, 10, 10, 11, 10, 11, 11, 11, 10, 11, 10, 11, 10, 11, 10, 11, 10, 11, 10, 10, 10, 10, 10, 10, 9, 10, 10, 10, 10, 10, 10, 11, 10, 11, 10, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 10, 11, 10, 10, 10, 10, 9, 10, 10, 10, 10, 11, 10, 11, 10, 11, 11, 11, 10, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 11, 11, 12, 11, 12, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 11, 10, 11, 11, 12, 11, 12, 11, 11, 10, 11, 11, 11, 10, 11, 10, 10, 9, 10, 10, 11, 10, 11, 11, 11, 10, 11, 11, 12, 11, 12, 11, 11, 10, 11, 11, 12, 11, 12, 12, 11, 11, 12, 12, 12, 11, 12, 11, 11, 10, 11, 11, 12, 11, 12, 12, 12, 11, 11, 12, 12, 11, 12, 11, 12, 11, 11, 11, 12, 11, 12, 11, 11, 11, 12, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 12, 11, 11, 11, 12, 11, 12, 12, 12, 11, 12, 11, 12, 11, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 11, 12, 11, 12, 11, 11, 11, 11, 11, 11, 10, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 11, 12, 11, 11, 11, 11, 10, 11, 11, 11, 11, 12, 11, 12, 11, 12, 12, 12, 11, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 12, 12, 12, 12, 11, 12, 12, 12, 12, 13, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 12, 12, 12, 13, 12, 13, 12, 12, 12, 13, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 13, 12, 12, 12, 13, 12, 13, 12, 12, 12, 13, 12, 13, 12, 13, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 12, 13, 12, 13, 12, 13, 12, 13, 12, 13, 12, 13, 12, 13, 13, 13, 12, 13, 13, 13, 12, 13, 12, 13, 12, 13, 13, 13, 12, 13, 13, 13, 12, 13, 12, 13, 12, 12, 12, 13, 12, 13, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 12, 13, 12, 12, 12, 12, 12, 13, 12, 13, 13, 13, 12, 13, 13, 13, 12, 13, 12, 12, 11, 12, 12, 13, 12, 13, 13, 13, 12};

int main()
{
    int n;
    while(scanf("%d", &n), n)
        printf("%d
", res[n]);
    return 0;
}