Hdu 2616 Kill the monster (Deep Search)

There are n skills. Each skill can only be used once. The monster has m points of blood and asks how many skills are required to kill the monster. Each skill has two values: a and B. a indicates the attack power. B indicates that when the volume of the monster's blood is less than or equal to B, the attack power of this skill can be changed to 2a. A little attack power can kill monsters with a little blood. Simple Deep Search added a pruning from the 421 MS instantly fell to 93 MS code:

#include <stdio.h>   #include <string.h>   struct node {      int M, spell;  } a[11];  int hp, n;  int vis[11];  int ans ;  void dfs(int k, int HP) {      int i;      if(k>=ans) return ;      if(HP<=0) {          if(ans>k)              ans = k;          return;      }      for(i=1; i<=n; i++)          if(!vis[i]) {              vis[i] = 1;              HP<=a[i].M? dfs(k+1,HP-a[i].spell*2): dfs(k+1,HP-a[i].spell);              vis[i] = 0;          }    }  int main() {      int i;      while(~scanf("%d%d",&n,&hp)) {          for(i=1; i<=n; i++)              scanf("%d%d",&a[i].spell,&a[i].M);          ans = 12;          memset(vis,0,sizeof(vis));          dfs(0,hp);          if(ans !=12) printf("%d\n",ans);          else printf("-1\n");      }      return 0;  }  #include <stdio.h>#include <string.h>struct node {    int M, spell;} a[11];int hp, n;int vis[11];int ans ;void dfs(int k, int HP) {    int i;    if(k>=ans) return ;    if(HP<=0) {        if(ans>k)            ans = k;        return;    }    for(i=1; i<=n; i++)        if(!vis[i]) {            vis[i] = 1;            HP<=a[i].M? dfs(k+1,HP-a[i].spell*2): dfs(k+1,HP-a[i].spell);            vis[i] = 0;        }}int main() {    int i;    while(~scanf("%d%d",&n,&hp)) {        for(i=1; i<=n; i++)            scanf("%d%d",&a[i].spell,&a[i].M);        ans = 12;        memset(vis,0,sizeof(vis));        dfs(0,hp);        if(ans !=12) printf("%d\n",ans);        else printf("-1\n");    }    return 0;}