手撕代码

二分法的查找

public int dicFind(int min,int max,int a[],int value){
        if (a[min] > value || a[max] < value){
            return -2;
        }
        int mid = (min+max)/2;
        if(min == max && a[min] != value){
            return -2;
        }
        if(a[mid]>value){
            return dicFind(min,mid,a,value);
        } else if(a[mid] < value){
            return dicFind(mid,max,a,value);
        } else {
            return mid;
        }

    }

单例-懒汉式

class A{
  private static A a = null;
  private A(){}
  public static A getInstance(){
    if(a == null){
      a = new A();
    }
    return a;
  }
}

单例-饿汉式

class B{
  private static B a = new B();
  private B(){}
  public static B getInstance(){
    return b;
  }
}

快速排序

public static void quickSort(int[] arr,int begin,int end){
  if(begin>=end) return;
  int point = data[begin];
  int i = begin + 1;
  int j = end;
  while(true){
    while(i<end&& point > data[i]){
      i++;
    }  
     while(j>begin && point < data[j]){
      j--;
    }  
     if(i<j){
        swap(data,i,j);
      } else {
        break;
      }
  }
  swap(data,begin,j);
  quickSort(data,begin,j-1);
  quickSort(data,j+1,end);
}
private static void swap(int[] data,i,j){
    if(i==j){
      return;
    }
    data[i] = data[i] + data[j];
    data[j] = data[i] - data[j];
    data[i] = data[i] - data[j];
}