uva 1374 Power Calculus

题目：Power Calculus

思路：

IDA*。

预先处理出1~1000的表，输入时再去查表。

估价函数：(Max2<<(maxd-x))<goal

代码：

#include<iostream>#include<cstdio>#include<cstring>#include<vector>#include<map>#include<algorithm>#include<sstream>#include<queue>#include<set>using namespace std;#define n 1000int m;int maxd;int f[n+5]= {0};int Abs(int x) {if(x<0) return -x;return x;}bool cmp(const int& a,const int& b) {return a>b;}int vec[n*5]={0};bool dfs(int goal,int x) {if(vec[x]==goal) return true;if(x==maxd) {return false;}int Max1=0,Max2=0;for(int i=0;i<=x;i++){if(vec[i]>Max2){Max1=Max2,Max2=vec[i];}}if((Max2<<(maxd-x))<goal) return false;for(int i=x; i>=0; i--) {vec[x+1]=vec[i]+vec[x];if(dfs(goal,x+1)) return true;vec[x+1]=vec[x]-vec[i];if(dfs(goal,x+1)) return true;}return false;}int main() {for(int i=2; i<=n; i++) {maxd=1;for( ; maxd<13 ; maxd++) {vec[0]=1;if(dfs(i,0)) break;}f[i]=maxd;}while(scanf("%d",&m)&&m) {printf("%d\n",f[m]);}return 0;}