二分查找算法详解-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_37112164/article/details/106411082

本文深入探讨了二分查找算法的三种实现方式：返回mid、返回left和返回right的二分查找模板。每种实现方式都有其独特的应用场景，通过详细的代码示例，读者可以更好地理解和掌握二分查找算法的核心思想。

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返回mid的二分查找模板：

int binary_search(int[] nums,int target){
	int left = 0,right = nums.length-1;
	while(left<=right){
		int mid = left+(right-left)/2;
		if(nums[mid] == target) return mid;
		else if(nums[mid] > target){
			right = mid - 1;
			从右端向mid逼近
		}
		else if(nums[mid] < target){
			left = mid + 1;
			从左端向mid逼近
		}
	}
	return -1;
}

返回left的二分查找模板：

int binary_search(int[] nums,int target){
	int left = 0, right = nums.length-1;
	while(left<=right){
		int mid = left+(right-left)/2;
		if(nums[mid] == target) right = mid-1;
		从右端向left逼近
		else if(nums[mid] > target){
			right = mid-1;
			从右端向left逼近
		}
		else if(nums[mid] < target){
			left = mid + 1;
		}
	}
	if(left>=length || nums[left]!=target){
		return -1;
	} 
	return left;
}

返回right的二分查找模板：

int binary_search(int[] nums,int target){
	int left = 0,right = nums.length-1;
	while(left<=right){
		int mid = left+(right-left)/2;
		if(nums[mid] == target) left = mid+1;
		从左端向right逼近
		else if(nums[mid] > target){
			right = mid-1;
		}
		else if(nums[mid] < target){
			left = mid+1;
			从左端向right逼近
		}
	}
	if(right<0 || nums[right]!=target){
		return -1;
	}
	return right;
}