java数据结构与算法1

数据结构的特性

最大子序列

public class maxsubnum {

	/**
	 * @param args最大子序列
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int arr[]={-1,4,5,1,-3,2};
		System.out.println(maxsubnumber(arr)+"");
	}
	public static int maxsubnumber(int arr[]){
		int maxsum=0;int thisum=0;
		for(int j=0;j<arr.length;j++){
			thisum+=arr[j];
			if(thisum>maxsum){
				maxsum=	thisum;
			}
			else if(thisum<0){
				thisum=0;
			}
		}
		
		return maxsum;
		
	}
}

折半查找算法

public class halfselect {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int arr[]={1,2,3,4,5,6,7,8};
		System.out.println(halfsel(arr,4)+"");
		}
		public static int halfsel(int arr[],int num){
			int low=0,high=arr.length-1;
			while(low<=high){
				int middle=(low+high)/2;
				if(arr[middle]<num)
					low=middle+1;
				else if(arr[middle]>num)
					high=middle-1;
				else return middle;
					
			}
			return 0;
		
			
		}
}

折半查找的是时间复杂度为O(logN) 循环次数最多为（logN-1）+2