Problem Statement 问题描述
When a stone is thrown across water, sometimes it will land on the water and bounce rather than falling in right away. Suppose that a stone is thrown a distance of n. On each successive bounce it will travel half the distance as the previous bounce (rounded down to the nearest integer). When it can not travel any further, it falls into the water. If, at any point, the stone lands on an obstruction rather than water, it will not bounce, but will simply deflect and fall into the water. Please look at the figure for further clarification (with black, red and green cells representing banks, obstructions and free water respectively). So, if the stone is thrown a distance 7, it will bounce and travel a distance of 3, then finally a distance of 1, having travelled a total distance of 11 (the green path in the figure). If a stone is thrown a distance of 8, it will reach the opposite bank, and if thrown at distances of 2 or 6 it will hit an obstruction during its travel. These are the three red paths in the figure.
You are given a String water. An ‘X’ represents an obstruction, while a ‘.’
represents water free from obstruction. You are to return an int representing
the maximum distance a stone can travel and finally fall in the water, without
hitting any obstructions, and without reaching the opposite bank (going beyond
the end of the string). You may choose any initial distance for the throw,
which starts from the left side of the string. A distance of 1 is the first
character of the string, etc. If no initial throw will result in the stone
landing in the water without hitting an obstruction, return 0.
给予一个 String 输入：water. 其内’X'字符代表礁石，’.’ 代表无礁石水面。你的程序
情形都必须排除。其中撞岸表征为 (字符串访问越上界). 你可以选择任何初始的投掷距离
int maxDistance(String water)
12 + 6 + 3 + 1 = 22, 为最佳结果.