Introduction to binary search in C# (code introduction)

This article uses an introductory case (code) of binary search to introduce to you what binary search is in C#? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Binary search: applicable to sorted arrays

1. Binary search (entry case)

static void Main(string[] args) {
	int[] myNums = {1,13,22,34,56,143,167,211,266,363,466,572,595,645,688,689,702,779,888,899,922};

	Console.WriteLine("我的数组是：");
	for(int i = 0; i < myNums.Length; i++) {
		Console.Write("{0} ", myNums[i]);
	}
	Console.WriteLine();

	//使用二分法从数组查找指定值
	//取得查找值在数组中的索引位置
	int QueryValueIndex = QueryFromTwoParts(688, myNums, 0, myNums.Length - 1);
	Console.WriteLine("--------------------------------------------------------");
	Console.WriteLine("查找值688在数组中的索引位置是:{0}", QueryValueIndex);
	Console.WriteLine("数组myNums索引位置{0}处的值是:{1}", QueryValueIndex, myNums[QueryValueIndex]);

	Console.ReadKey();
}

//该方法返回的是查找值在数组中的索引位置
private static int QueryFromTwoParts(int QueryValue, int[] nums, int leftIndex, int rightIndex) {
	//计算数组中间值的在数组中的索引位置
	int midValueIndex = (leftIndex + rightIndex + 1) / 2;

	//取得数组中间索引位置处的值
	int midValue = nums[midValueIndex];

	//比较中间值与查找值的大小，确定下一步该怎样继续查询
	if(QueryValue == midValue) {
		return midValueIndex;
	} else if(QueryValue < midValue) {
		return QueryFromTwoParts(QueryValue, nums, leftIndex, midValueIndex);
	} else {
		return QueryFromTwoParts(QueryValue, nums, midValueIndex, rightIndex);
	}

}

2. Code running results:

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