數據結構與算法-->遞歸

遞歸打印數字：

package test;

public class Recursion1 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		printOut(345423456);
	}
	
	/**
	 * 
	 * @param n
	 */
	public static void printOut(int n){
		
		if(n > 10){
			printOut(n/10); // 遞歸體，總能想一個基準狀況靠攏
		}
		System.out.print(n%10);// 基準狀況
	}

}

遞歸求解最大子序列：

public static int maxSubSum4(int[] a,int left, int right){
		
		int leftMaxSum=0,rightMaxSum=0,leftTempSum=0,rightTempSum=0;
		int center = (left+right)/2;
		
		//基本狀況
		if(left == right){
			return a[left]>0?a[left]:0;
		}
		
		//左邊包括最後一個元素的最大和
		for(int i=center; i>=left; i--){
			leftTempSum += a[i];
			if(leftTempSum>leftMaxSum){
				leftMaxSum = leftTempSum;
			}
		}
		
		//右邊包括第一個元素的最大和
		for(int i=center+1; i<=right; i++){
			rightTempSum += a[i];
			if(rightTempSum>rightMaxSum){
				rightMaxSum = rightTempSum;
			}
		}
		
		//左邊最大和(遞歸)
		int leftMax = maxSubSum4(a, left, center);
		//右邊最大和(遞歸)
		int rightMax = maxSubSum4(a, center+1, right);
		
		return max3( leftMax, rightMax,
				leftMaxSum + rightMaxSum );
		
		
	}
	
	private static int max3( int a, int b, int c )
    {
        return a > b ? a > c ? a : c : b > c ? b : c;
    }

遞歸折半查找：

public class Dgzbcz {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Integer[] arr = {-3,-2,-2,-1,2,4,5,6};
		int index = bannarySearch(arr,-2,0,arr.length-1);
		System.out.println(index);
	}
	
	
	public static <AnyType extends Comparable<? super AnyType>> int bannarySearch(AnyType[] a,AnyType x,int low,int hight){
		
		// 不斷推動
		int mid = (low+hight)/2;
		
		// 基本狀況1
		if(a[mid].compareTo(x)==0){
			return mid;
		}
		// 基本狀況2
		if(low == hight){
			return -1;
		}
		
		// 不斷推動
		return a[mid].compareTo(x)>0?bannarySearch(a,x,low,mid):bannarySearch(a,x,mid+1,hight);
		
	}

}