Array Packing
Description
You are given an array of up to four non-negative integers, each less than 256.
Your task is to pack these integers into one number M in the following way:
- The first element of the array occupies the first 8 bits of M;
- The second element occupies next
8bits, and so on.
Return the obtained integer M.
Note: the phrase “first bits of M” refers to the least significant bits of M - the right-most bits of an integer. For further clarification see the following example.
Example
For a = [24, 85, 0], the output should be
arrayPacking(a) = 21784.
An array [24, 85, 0] looks like [00011000, 01010101, 00000000] in binary.
After packing these into one number we get 00000000 01010101 00011000 (spaces are placed for convenience), which equals to 21784.
Input/Output
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[execution time limit] 4 seconds (js)
-
[input] array.integer a
Guaranteed constraints:
1 \leq a.length \leq 4,
0 \leq a[i] \le 256. -
[output] integer
[JavaScript (ES6)] Syntax Tips
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// Prints help message to the console
// Returns a string
function helloWorld(name) {
console.log("This prints to the console when you Run Tests");
return "Hello, " + name;
}
Solution
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function arrayPacking(a) {
while (a.length < 4)
a.push(0);
return a[3] << 24 | a[2] << 16 | a[1] << 8 | a[0];
}