假设
-
你有一个数字数组作为输入
-
对makeRandom 的每次调用都应从您的数组中随机选择两个数字并输出总和
-
随后对makeRandom 的每次调用都不应使用已使用的任何号码 (id)
list = [1,1,2,3,4,5];
// The number 1 could be used twice (but only in different calls to makeRandom)
// The numbers 2,3,4,5 can only be used once
list = [1,1];
// Shouldn't work because 1 == 1
JS 代码
var list = [1,2,3,4,5,6,7,8,9]; // Your seed list
var usable = list.slice(0); // Copy of your seed list {which we will alter with makeRandom}
function makeRandom(){
// Check it's possible...
let counts = {}; // Create object to count unique numbers
for (var i = 0; i < usable.length; i++) {
counts[usable[i]] = 1 + (counts[usable[i]] || 0); // Iterate array and fill counts
}
if(Object.keys(counts).length < 2){ // Check there are at least two unique numbers
console.log("List is too short!"); // Log error if <2
return false; // Exit function if <2
}
// Get random numbers and output sum...
let id = Math.floor(Math.random() * usable.length) // Randomly select an id from usable numbers
let a = usable[id]; // Set first number
usable.splice(id, 1); // Remove 1st number from usable numbers
let b;
while(true){ // Loop until numbers are different
id = Math.floor(Math.random() * usable.length); // Randomly select an id from usable numbers
b = usable[id]; // Set second number
if(a !== b)break; // Check 1st number isn't the same as the second number
}
usable.splice(id, 1); // Remove 2nd number from usable numbers
// console.log(a + " + " + b + " = " + (a+b)); // Log for debugging if required
return a+b; // Return sum of 1st and 2nd numbers
}
注意：为了便于理解，我已经完整地输入了 while 循环；它可以缩短使用 do...while(...):
let b;
do b = list[Math.floor(Math.random() * list.length)]; // Set second number
while(a==b) // Re-set second number if a == b OR if b was used in the last call to makeRandom
示例
var list = [1,2,3,4,5,6,7,8,9];
var usable = list.slice(0);
function makeRandom(){
let counts = {};
for (var i = 0; i < usable.length; i++) {
counts[usable[i]] = 1 + (counts[usable[i]] || 0);
}
if(Object.keys(counts).length < 2){
console.log("List is too short!");
return false;
}
let id = Math.floor(Math.random() * usable.length)
let a = usable[id];
usable.splice(id, 1);
let b;
while(true){
id = Math.floor(Math.random() * usable.length);
b = usable[id];
if(a !== b)break;
}
usable.splice(id, 1);
console.log(a + " + " + b + " = " + (a+b));
return a+b;
}
// Make several calls to function
makeRandom();
makeRandom();
makeRandom();
makeRandom();
makeRandom();
makeRandom();
// Change the seed lists
var list = [1,1,1,1,1,9];
var usable = list.slice(0);
// Make several calls to function
makeRandom();
makeRandom();
makeRandom();
示例输出
__Example 1__
list = [1,2,3,4,5,6,7,8,9]; // Example list used
// console.log return
> makeRandom(); // 4 + 2 = 6 6
> makeRandom(); // 1 + 8 = 9 9
> makeRandom(); // 9 + 3 = 12 12
> makeRandom(); // 6 + 7 = 13 13
> makeRandom(); // List is too short! false
> makeRandom(); // List is too short! false
__Example 2__
list = [1,1,1,1,1,9]; // Example list used
// console.log return
> makeRandom(); // 1 + 9 = 10 10
> makeRandom(); // List is too short! false
> makeRandom(); // List is too short! false
替代方案
查看了您的问题的更新...
我不清楚这些数字是否只能使用一次或如果它们不能背靠背使用。
list = [1,2,3,4,5];
// Choose from // Chosen
> makeRandom(); // 1, 2, 3, 4, 5 // 1, 4
> makeRandom(); // 2, 3, 5 // 2, 3
> makeRandom(); // 1, 4, 5 // 1, 5
如果是这样，那么以下内容可能更有用
var list = [1,2,3,4,5,6,7,8,9]; // Your seed list
var used = []; // Last used pair of numbers
function makeRandom(){
// Check it's possible...
let counts = {}; // Create object to count unique numbers
for (var i = 0; i < list.length; i++) {
counts[list[i]] = 1 + (counts[list[i]] || 0); // Iterate array and fill counts
}
if(Object.keys(counts).length < 4){ // Check there are at least four unique numbers: any less and we'll end up in an infinite loop on the second call of makeRandom
console.log("List is too short!"); // Log error if <2
return false; // Exit function if <2
}
// Get random numbers and output sum...
let a;
do a = list[Math.floor(Math.random() * list.length)]; // Set first number
while(used.includes(a)) // Reset first number if a was used in the last call to makeRandom
let b;
do b = list[Math.floor(Math.random() * list.length)]; // Set second number
while(a==b || used.includes(b)) // Re-set second number if a == b OR if b was used in the last call to makeRandom
used = [a, b]; // Set last used numbers
console.log(a + " + " + b + " = " + (a+b)); // Log for debugging if required
return a+b; // Return sum of 1st and 2nd numbers
}
// Make several calls to function
makeRandom();
makeRandom();
makeRandom();
makeRandom();
makeRandom();
makeRandom();
// Change the seed lists
var list = [1,2,3,4];
// Make several calls to function
// Notice with only 4 numbers once the first pair is selected (e.g. 1 & 3) the pattern cycles 1,3 -> 2,4 -> 1,3 -> 2,4
makeRandom();
makeRandom();
makeRandom();