Java递归小程序

 

/**
 * 三角数字之和 ...5+4+3+2+1
 * @param n
 * @return
 */
public int triangle(int n){
    if(n==1){
        return 1;
    }
    return n+triangle(n-1);
}

/**
 * 阶乘 5!
 * @param n
 * @return
 */
public int factorial(int n){
    if(n==1){
        return 1;
    }
    return n*factorial(n-1);
}

/**
 * 递归二分查找
 * @param a
 * @param findKey
 * @return
 */
public int recFind(int[] a,int findKey,int low,int high){
    int mid=(low+high)/2;
    if(a[mid]==findKey){
        return mid;
    }else if(low>mid){
        return -1;
    }else{
        if(a[mid]<findKey){
            return recFind(a,findKey,mid+1,high);
        }else{
            return recFind(a,findKey,low,mid-1);
        }
    }
}

/**
 * 汉诺塔问题
 * @param topN
 * @param from
 * @param inter
 * @param to
 */
public void doTower(int topN,char from,char inter,char to){
    num++;
    if(topN==1){
        System.out.println("Disk 1 from "+from+" to "+to);
    }else{
        doTower(topN-1,from,to,inter);
        System.out.println("Disk "+topN+" from "+from+" to "+to);
        doTower(topN-1,inter,from,to);
    }
    System.out.println(num);
}