hdu 2616 Kill the monster(stl全排列+暴力)
Kill the monster
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 502 Accepted Submission(s): 345
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.
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).
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.
Sample Input
3 100
10 20
45 89
5 40
3 100
10 20
45 90
5 40
3 100
10 20
45 84
5 40
Sample Output
3
2
-1
分析:
(1)因为数据比较少,每一组最多有是个数据,可以用全排列暴力计算找出最小的组合
(2)这里借助于stl算法库中的next_permutation()全排列算法。暴力把所有的排列方法计算一遍。然后找出最小的组合方法。
#include <iostream> #include <stdio.h> #include <algorithm> using namespace std; int main() { int o[10],a[10],m[10]; int n,M,count,min; while(cin>>n>>M) { for(int i=0;i<n;i++) cin>>a[i]>>m[i]; for(int i=0;i<n;i++) o[i] = i; min = 100; do{ count = 0; int tem = M; for(int i=0;i<n;i++) { count++; if(tem<=m[o[i]]) tem -= a[o[i]]*2; else tem -= a[o[i]]; if(tem<=0) { if(count<min) min = count; break; } } }while(next_permutation(o,o+n)); if(min==100)printf("-1\n"); else printf("%d\n",min); } return 0; }
posted on 2012-10-06 18:40 NewPanderKing 阅读(843) 评论(0) 编辑 收藏 举报