Depend onjsThe basis for generating all random numbers is(), This method is quite special. The generated random number falls in the interval [0,1). If you perform an operation once,jsOnly one interval similar to [n,m) can be generated, which is closed left and open right. Therefore, when there are some special needs, some other operations are necessary. The following is a simple analysis of various needs:
Generate integers in any interval
1. Fully closed interval [n,m]
This is the most common, the long list of formulas that everyone knows:(()*(m-n+1))+n;It is the method to generate this fully closed interval. Many people know this formula, but few people really think it through. Create a range of [0,m-n+1) like this, close the left and right, and then use()Take any integer between [0,m-n] (it is very important to understand this step), and then add the left endpoint of the interval to become any integer within [n,m] to achieve the goal.
Speaking of this, one thing must be mentioned. Just search for js to generate random numbers. Many articles will use it.()or()These two methods, such as generating any integer in the fully closed [n,m] interval,(()*(m-n))+n;or(()*(m-n))+n;I feel that the most important thing about random numbers is two random words, and the probability of each value must be equal. This is very important for some specific occasions, such as lottery (there are lottery draws in annual meetings).
()The problem is that n<<m≈x, x is a number other than the endpoint. If the interval is large enough, n cannot be retrieved. The probability of m and x is almost equal, because the point m cannot be retrieved, so the probability is relatively small.()The problem is that n≈m=x/2, and the reason is similar to the previous one. If you don’t understand, you can draw a coordinate axis by yourself. It’s very clear.
2. Fully open interval (x,y)
In fact, as long as you remember the fully closed interval above, the opening and closing of all other intervals can be pushed by it. The process is as follows:
(x,y) ＝＝[x+1,y-1]; that is to say n=x+1; m=y-1; substitute it into the above formula to get:(()*(y-x-1))+x+1;
3. Close left and open right [x,y)
Similarly, [x,y) ＝＝ [x,y-1]; substituting to obtain:(()*(y-x))+x;
4. Open left and close right (x,y]
(x,y]==[x+1,y]; substitute to obtain:(()*(y-x))+x+1;
Generate floating point numbers in any interval
This kind of thing is used less in reality, but it is also quite interesting.
[n,m)
This is the simplest because it is consistent with the characteristics of random.()*(m-n)+n;
Because of this characteristic of random, it is more difficult to get floating point numbers in other intervals. It takes some judgment to meet the requirements. The idea is the same as the one with integers above. The code is as follows:
function fullClose(n,m) { //[n,m]
var result = ()*(m+1-n)+n;
while(result>m) {
result = ()*(m+1-n)+n;
}
return result;
}
function fullOpen(n,m) { // (n,m)
var result = ()*(m-n)+n;
while(result == n) {
result = ()*(m-n)+n;
}
return result;
}
function leftOpen(n,m) { // (n,m]
var result = ()*(m-n+1)+n-1;
while(result<n) {
result = ()*(m-n+1)+n-1;
}
return result;
}
The above is all the content of this article. I hope it will be helpful to everyone's study and I hope everyone will support me more.