Kill the monster

Kill the monster

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<n<10, 1<m<10^7), express how many spells yifenfei has.
Next n line , each line express one spell. (Ai, Mi).(0<Ai,Mi<=m).

 

Output

For each test case output one integer that how many spells yifenfei should use at least. If yifenfei can not kill the monster output -1. 

#include<stdio.h>int m,n,minn;int a[10],b[10],num[10];int dfs(int jishu,int hp){    if(jishu>m)      return 0;    if(hp<=0)    {        if(minn>jishu)            minn=jishu;        return 0;    }    for(int i=0;i<m;i++)    {        if(num[i]==0)        {            num[i]=1;            if(hp<=b[i])            {                dfs(jishu+1,hp-2*a[i]);            }            else            dfs(jishu+1,hp-a[i]);            num[i]=0;        }    }       return 0;}int main(){    while(~scanf("%d%d",&m,&n))    {        for(int i=0;i<m;i++)        {            scanf("%d%d",&a[i],&b[i]);            num[i]=0;        }        minn=12;        dfs(0,n);        if(minn==12)        {            printf("-1\n");        }        else        {            printf("%d\n",minn);        }    }}