hdu 2616 Kill the monster(dfs+最优化剪枝+迭代加深搜索)

最新推荐文章于 2020-11-01 10:55:08 发布

原创最新推荐文章于 2020-11-01 10:55:08 发布 · 750 阅读

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#C++ #dfs #最优化剪枝 #迭代加深搜索

本文探讨了一款名为‘杀怪’的游戏，通过输入怪物生命值和英雄拥有的多种魔法攻击，玩家需要计算最少使用多少次攻击才能击败怪物。文章深入分析了问题的解决策略，并介绍了使用迭代加深搜索等算法优化解决方案。

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Kill the monster

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 959 Accepted Submission(s): 695

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.

Sample Input

Sample Output

3
2
-1

题目分析:当出现可以双倍的时候,只要不出现单倍的能够一次性解决boss的情况,都只有在先用掉双倍的情况才是最优,利用这一求取最优的性质剪枝,利用迭代加深搜索即可