HDU 2616 Kill the monster 简单DFS

Kill the monster
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1186 Accepted Submission(s): 817

Problem Description
There is a mountain near yifenfei’s hometown. On the mountain lived a big monster. As a hero in hometown, yifenfei wants to kill it.
Now we know yifenfei have n spells, and the monster have m HP, when HP <= 0 meaning monster be killed. Yifenfei’s spells have different effect if used in different time. now tell you each spells’s effects , expressed (A ,M). A show the spell can cost A HP to monster in the common time. M show that when the monster’s HP <= M, using this spell can get double effect.

Input
The input contains multiple test cases.
Each test case include, first two integers n, m (2

#include <iostream>#include <cstring>using namespace std;int n,m;int Ai[10],Mi[10];int used[10];int mina;void dfs(int deep,int hp){    if(hp<=0)    {        if(mina>=deep)        mina=deep;        return;             }    for(int i=0;i<n;i++)    {        if(used[i]==1)        continue;        used[i]=1;        if(hp<=Mi[i])        dfs(deep+1,hp-2*Ai[i]);        else         dfs(deep+1,hp-Ai[i]);        used[i]=0;    }}int main(int argc, char *argv[]){    while(cin>>n>>m)    {        for(int i=0;i<n;i++)        cin>>Ai[i]>>Mi[i];        memset(used,0,sizeof(used));        mina=99;        dfs(0,m);        if(mina==99)        cout<<-1<<endl;        else         cout<<mina<<endl;    }           return 0;}