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原题目网址：http://acm.pku.edu.cn/JudgeOnline/problem?id=1548
Your company provides robots that can be used to pick up litter from fields after sporting events and concerts. Before robots are assigned to a job, an aerial photograph of the field is marked with a grid. Each location in the grid that contains garbage is marked. All robots begin in the Northwest corner and end their movement in the Southeast corner. A robot can only move in two directions, either to the East or South. Upon entering a cell that contains garbage, the robot will pick it up before proceeding. Once a robot reaches its destination at the Southeast corner it cannot be repositioned or reused. Since your expenses are directly proportional to the number of robots used for a particular job, you are interested in finding the minimum number of robots that can clean a given field. For example, consider the field map shown in Figure 1 with rows and columns numbered as shown and garbage locations marked with a 'G'. In this scheme, all robots will begin in location 1,1 and end in location 6, 7.
Your task is to create a program that will determine the minimum number of robots needed to pick up all the garbage from a field.
Your company provides robots that can be used to pick up litter from fields after sporting events and concerts. Before robots are assigned to a job, an aerial photograph of the field is marked with a grid. Each location in the grid that contains garbage is marked. All robots begin in the Northwest corner and end their movement in the Southeast corner. A robot can only move in two directions, either to the East or South. Upon entering a cell that contains garbage, the robot will pick it up before proceeding. Once a robot reaches its destination at the Southeast corner it cannot be repositioned or reused. Since your expenses are directly proportional to the number of robots used for a particular job, you are interested in finding the minimum number of robots that can clean a given field. For example, consider the field map shown in Figure 1 with rows and columns numbered as shown and garbage locations marked with a 'G'. In this scheme, all robots will begin in location 1,1 and end in location 6, 7.
Your task is to create a program that will determine the minimum number of robots needed to pick up all the garbage from a field.
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SamuelKevin 2006-06-29
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哦 不对是贪心吧 寒
SamuelKevin 2006-06-29
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English不行 不过粗略看了一下原题 感觉貌似用到回溯
xyq1986 2006-06-29
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这题没做过……不过20分要个算法也太少了吧……
矮胖挫 2006-06-29
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感谢,说的很明白了
sharpdew 2006-06-29
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类似在一个N*N的网格中划路径，对于每条路径来说要使得路径上遇到的垃圾尽量多，对于整个问题来说要使得能覆盖垃圾的所有路径最少。
路径只能从(1,1)开始到(N,N)点结束，且每走一步点的横坐标和纵坐标至少有一个加1。
这个问题可以通过把所有垃圾对应的点连接成一个图来解决，这个图中从开始点到结束点的所有路径就是所要求的机器人数目。连线的规则如果一个点的坐标均不大于另外一个点的坐标，则这两个点之间可以连一条线。
路径只能从(1,1)开始到(N,N)点结束，且每走一步点的横坐标和纵坐标至少有一个加1。
这个问题可以通过把所有垃圾对应的点连接成一个图来解决，这个图中从开始点到结束点的所有路径就是所要求的机器人数目。连线的规则如果一个点的坐标均不大于另外一个点的坐标，则这两个点之间可以连一条线。
yingge 2006-06-29
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ACM的题吧，应该有sample input和sample output才对啊
