Program ape to find a job also have to test IQ? Alibaba's technical department interviews for intelligence questions

Now programmers find a job list has a hard programming technology, a good code is not enough, many companies in the recruitment will test the interviewer's way of thinking, IQ, emotional intelligence and so on, through a variety of unexpected questions, such as Alibaba's technical department interview questions will often involve some intellectual problems.

W3Cschool has collected some for the program apes here so that we can be comfortable during the interview.

The title begins:

1, a group of people to dance, each wearing a hat on their heads. T here are only two kinds of hats in black and white, and at least one in black. E veryone can see the color of other people's hats, but they can't see their own. T he host first let everyone see what other people wear on their heads, and then turn off the lights, if someone thinks they are wearing a black hat, hit themselves a slap. T urn off the lights for the first time, no sound. S o turn on the lights again, we look again, turn off the lights are still silent. I t was not until the third time that the lights were turned off that the sound of crackling slaps rang out. How many people are wearing black hats?

----答案----
有三个人戴黑帽。假设有N个人戴黑，当N=1时，戴黑人看见别人都为白则能肯定自己为黑。于是第一次关灯就应该有声。可以断定N>1。对于每个戴黑的人来说，他能看见N-1顶黑帽，并由此假定自己为白。但等待N-1次还没有人打自己以后，每个戴黑人都能知道自己也是黑的了。所以第N次关灯就有N个人打自己。

2, there are two uneven distribution of incense, incense burned out time is an hour, what method can you use to determine a period of 15 minutes?

----答案----
香a点燃一头，香b点燃两头。等香b烧完时，时间过去了30分钟。再把香a剩下的另一头也点燃。从这时起到a烧完的时间就是15分钟。

3, there are three people to stay in the hotel, live in three rooms, each room $10, so they paid the boss a total of $30, the next day, the boss felt that three rooms only need $25 yuan is enough, so asked the younger brother to return $5 to three guests, Who knows the little brother greedy, only returned $1 per person, they secretly took $2, so that it is equal to the three guests each spent nine yuan, so three people spent a total of $27, plus the little brother swallowed $2 alone, a total of $29. But when the three of them paid a total of $30, what about $1?

----答案----
典型的偷换概念。事实上3人只付出了27元，老板得了25元，小弟拿了2元。

4, a manager has three daughters, three daughters add up to 13, three daughters of age multiplied equal to the manager's own age, there is a subordinate already know the manager's age, but still can not determine the manager's three daughters age, when the manager said that only one daughter's hair is black, and then the subordinate knows the manager's three daughters age. W hat are the ages of the three daughters, please? Why?

----答案----
三女的年龄应该是2、2、9。因为只有一个 孩子黑头发，即只有她长大了，其他两个还是幼年时期即小于3岁，头发为淡色。再结合经理的年龄应该至少大于25。

5, imagine you in front of the mirror, please ask, why the image in the mirror can be upside down, but can not be upside down?

----答案----
镜像对称的轴是人的中轴

6, there are two blind people, they each bought two pairs of black socks and two pairs of white socks, eight pairs of socks cloth, the same size, and each pair of socks have a trademark paper attached. T wo blind men accidentally mixed eight pairs of socks together. How can each of them get back two pairs of black socks and white socks?

----答案----
将每对袜子拆开一人一只。

7, you have a bucket of jelly, which has yellow, green, red three, close your eyes, grab two jelly of the same color. How many grabs will make sure you have two jellys of the same color?

----答案----
4个。数量＞颜色种类。颜色必重复。

8, one train left Los Angeles at 15 kilometers per hour for New York, and another train at 20 kilometers per hour from New York to Los Angeles. If there is a bird that starts at 30 km/h with two trains, departs from Los Angeles, meets another car and returns, flying back and forth between the two trains until the two trains meet, how long has the bird flown?

----答案----
设洛杉矶到纽约的铁路长为A公里。则两辆火车到相遇用了A/（15+20）小时，也就是小鸟飞行的时间。所以小鸟飞行的距离就是速度×时间=30×A/35=6/7的洛杉矶到纽约的铁路长。

9. If every 3 empty beer bottles can be exchanged for a bottle of beer, someone buys 10 bottles of beer, then how many bottles of beer can he drink?

----答案----
喝完10瓶后用9个空瓶换来3瓶啤酒(喝完后有4个空瓶）喝完这三瓶又可以换到1瓶啤酒（喝完后有2个空瓶）这时他有2个空酒瓶，如果他能向老板先借一个空酒瓶，就凑够了3个空瓶可以换到一瓶啤酒，把这瓶喝完后将空瓶还给老板就可以了。所以他最多可以喝10+3+1+1=15瓶

10, you have two cans, 50 red pinballs, 50 blue pinballs, randomly select a jar, randomly select a pinball into the jar, how to give the red pinball the greatest chance of selection? What is the exact chance of getting a red ball in your plan?

----答案----
1/2的几率。先选出球在选罐子。这样罐子其实对球的颜色无影响。

11, two rings, the radius is 1 and 2, small circle inside the large circle around the circle week, ask the small circle itself turned for a few weeks? What if the outer part of the large circle turns itself for a few weeks?

----答案----
无论内外，小圆转两圈。

12, you have four cans of pills, each pill has a certain weight, contaminated pills are not contaminated weight of 1. Weigh only once, how to judge which can of medicine is contaminated?

----答案----
1号罐取1丸，2号罐取2丸，3号罐取3丸，4号罐取4丸，称量该10个药丸，比正常重量重几就是几号罐的药有问题。

13, for a batch of numbers 1 to 100, all switches facing up (on) the lamp to do the following operations: all 1 multiple in the opposite direction to dial the switch once; Q: Finally, the number of the lights that are off.

----答案----
有10盏灯为灭，分别为1、4、9、16、25、36、49、64、81、100号。因为：每个质数能被1和自身整除，所以质数的灯是亮的。设一个合数能被N个数整除，N必然是个偶数。对于非某数平方的合数来说，将被开关N次也就是偶数次，灯保留为亮；对于上面列出的平方数，则只被开关N-1次，所以灯是灭的。