如何为较长的数字数组提高算法性能? [英] How do I increase the algorithm performance for longer array of numbers?
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问题描述
感谢您的光临。
计算有序数字数组中小于4的数字。
Count how many numbers are less than 4 in an ordered array of numbers.
如何做我可以为更长的数字数组提高算法性能?提高计算速度。二进制搜索有帮助吗?输出?
How do I increase the algorithm performance for longer array of numbers? Increase the calculation speed. Does binary search help? Outputs?
public static int CountNumbers(int[] sortedArray, int lessThan)
{
int count = 0;
for (int i = 0, len = sortedArray.Length; i < len; i++)
if (sortedArray[i] < lessThan)
count++;
else return count;
return count;
}
Assert.AreEqual(SortedSearch.CountNumbers(new int[] { 1, 3, 5, 7 }, 4), 2);
推荐答案
您应使用 Array .BinarySearch
static int CountNumbers(int[] sortedArray, int lessThan)
{
if (sortedArray[0] >= lessThan) return 0;
int lengthOfArray = sortedArray.Length;
if (lengthOfArray == 0) return 0;
if (sortedArray[lengthOfArray - 1] < lessThan) return lengthOfArray;
int index = Array.BinarySearch(sortedArray, lessThan);
if (index < 0)
return ~index;
// Find first occurrence in case of duplicate
for (; index > 0 && sortedArray[index - 1] == lessThan; index--) ;
return index;
}
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