leetcode简单题目两道(5)
2017-04-24 00:23
197 查看
Problem Given an integer (signed 32 bits), write a function to check whether it is a power of 4. Example: Given num = 16, return true. Given num = 5, return false. Follow up: Could you solve it without loops/recursion? Code class Solution { public: bool isPowerOfFour(int num) { return (num > 0) && ((num & (num - 1)) == 0) && ((num - 1) % 3 == 0); } }; 说明 利用了2的指数与本身减1相与为0,以及4的指数减1,必定能整除3; class Solution { public: bool isPowerOfFour(int num) { return (num > 0) && ((num & (num - 1)) == 0) && ((num & 0x55555555)); } }; 说明 利用了2的指数与本身减1相与为0,以及4的指数在16进制中的位置0x55555555,前者确定只有一个1,后者确定这个1肯定是4的指数的位置;
problem You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called "bulls") and how many digits match the secret number but locate in the wrong position (called "cows"). Your friend will use successive guesses and hints to eventually derive the secret number. Example: Secret number: "1807" Friend's guess: "7810" Hint: 1 bull and 3 cows. (The bull is 8, the cows are 0, 1 and 7.) Write a function to return a hint according to the secret number and friend's guess, use A to indicate the bulls and B to indicate the cows. In the above example, your function should return "1A3B". Please note that both secret number and friend's guess may contain duplicate digits, for example: Secret number: "1123" Friend's guess: "0111" In this case, the 1st 1 in friend's guess is a bull, the 2nd or 3rd 1 is a cow, and your function should return "1A1B". You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal. Code class Solution { public: string int2str(int int_temp) { stringstream stream; stream << int_temp; return stream.str(); } string getHint(string secret, string guess) { if(secret.size() == 0 || guess.size() == 0) { return 0; } int res1 = 0, res2 = 0, tmp; map<char, int> map1, map2; for(int i = 0; i < secret.size(); i++) { if (secret[i] == guess[i]) { res1++; } else { map1[secret[i]]++; map2[guess[i]]++; } } map<char,int>::iterator it; for(it=map1.begin();it!=map1.end();++it) { if (it->second < map2[it->first]) { tmp = it->second; } else { tmp = map2[it->first]; } res2 += tmp; } return int2str(res1) + "A" + int2str(res2) + "B"; } }; 一次遍历,不解释,哈哈。
相关文章推荐
- leetcode简单题目两道(3)
- leetcode简单题目两道(2)
- leetcode简单题目两道(4)
- leetcode -- Invert Binary Tree -- 简单题目看看
- leetcode -- First Missing Positive -- 简单trick题目
- 【Leetcode】碰到一道脑残leetcode,比之前觉得简单的还简单。。。一下还两道……Search in Rotated Sorted Array I和II
- 异或解决LeetCode两道算法题目
- leetcode -- Text Justification -- string操作的题目,思路简单,但是难以写对
- 两道简单的题目
- leetcode 595. Big Countries(SQL,最简单的leetcode题目)38
- leetcode -- Unique Paths I &&II-- 典型DP 题目,简单要看
- 贡献两道简单的leetcode
- LeetCode中的两道动态规划题目
- leetcode -- Range Sum Query 2D - Immutable -- 简单DP题目
- Leetcode两道小题目python试水
- Leetcode--两道简单的二进制问题
- 283. Move Zeroes——LeetCode(挪“零”)(简单题目)
- leetcode题解-Dynamic Programming简单类别题目汇总
- 微软面试简单算法题目
- 简单的加密题目(公钥私钥)