Count Sum Of Two Representations 2
Description
Given integers n
, l
and r
, find the number of ways to represent n
as a sum of two integers A
and B
such that l ≤ A ≤ B ≤ r
.
Example
For n = 6
, l = 2
, and r = 4
, the output should be
countSumOfTwoRepresentations2(n, l, r) = 2
.
There are just two ways to write 6
as A + B
, where 2 ≤ A ≤ B ≤ 4: 6 = 2 + 4
and 6 = 3 + 3
.
Input/Output
-
[execution time limit] 4 seconds (js)
-
[input] integer n
A positive integer.
Guaranteed constraints:
5 \leq n \leq 10^9
. -
[input] integer l
A positive integer.
Guaranteed constraints:
1 \leq l \leq r
. -
[input] integer r
A positive integer.
Guaranteed constraints:
1 \leq r \leq 10^9
,
r-l \leq 10^6
. -
[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 countSumOfTwoRepresentations2(n, l, r) {
if (2 * r < n || 2 * l > n) return 0;
var min = Math.max(l, n - r);
var max = Math.min(r, n - l);
var mid = Math.floor((max + min) / 2);
return mid - min + 1;
}