0 threshold takes you to know two-point search

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1. What is binary search ？

Binary search is also called half search , Is to find an element in an ordered array .

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2. The logic of binary search

The principle is simple , Take the target value every time （ use k Express ） Data in the middle of the array （ use arr[mid] Express ,mid Represents the index value in the middle of the array ） Compare , If k Greater than arr[mid], So the left subscript left=mid+1, Continue to k And greater than arr[mid] Compare the values of the middle position of the part ; If k Less than arr[mid], Then the right subscript right=mid-1, Continue to k And less than arr[mid] Compare the middle position value of the part .

 

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int main() {
	int a[] = { 1,2,3,4,5,6,7,8,9,10 };
	int sz = sizeof(a) / sizeof(a[0]);// Count the number of elements in an array 
	int left = 0;// Left subscript 
	int right = sz - 1;// Right subscript 
	int k = 7;// The element to look for 
	while (left <= right) {
		int mid = (left + right) / 2;// Find the middle subscript of the array 
		if (a[mid] < k) {
			left = mid + 1;
		}
		else if (a[mid] > k) {
			right = mid - 1;
		}
		else {
			printf(" eureka , The subscript is :%d\n", mid);
			break;
		}
	}
	if (left > right)
		printf(" Can't find \n");
	return 0;
}