344.[字符串反转] Reverse String

这是我的第一篇Leetcode刷题Note。
2016年07月14日

题目内容

Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

原string翻转的方法

class Solution {
public:
    string reverseString(string s) {
        char tmp;
        if(s.length() != 0)
            for(int i = 0, j = s.length()-1; i < j; i++, j--){
                tmp = s[i];
                s[i] = s[j];
                s[j] = tmp;
            }
        return s;  
    }
};

新建一个string的方法

class Solution {
public:
    string reverseString(string s) {
        string rst = s;//must give rst a length
        int p = 0;
        if(s.length() != 0)
            for(int i = s.length()-1 ;i >= 0;i--){
                rst[p] = s[i]; 
                p++;
            }
        return rst; 
    }
};

事实上，我是从昨天开始被Py点拨刷Leetcode的，第一道题是我写过最短的代码，记录如下：

292. Nim Game

You are playing the following Nim Game with your friend: There is a heap of stones on the table, each time one of you take turns to remove 1 to 3 stones. The one who removes the last stone will be the winner. You will take the first turn to remove the stones.

Both of you are very clever and have optimal strategies for the game. Write a function to determine whether you can win the game given the number of stones in the heap.

For example, if there are 4 stones in the heap, then you will never win the game: no matter 1, 2, or 3 stones you remove, the last stone will always be removed by your friend.

整除4得解

class Solution {
public:
    bool canWinNim(int n) {
        return n % 4; 
    }
};

等以后做到升级版Nim Game的时候再详细体会~