常用排序算法-java实现(插入,快排)
1、插入排序算法
/** Simple insertion sort.* @param a an array of Comparable items.*/public static void insertionSort(Comparable[] a){ for(int p=1; p < a.length ;p++){ Comparable tmp = a[p];//临时变量 int j = p; for(; j>0 && tmp.compareTo(a[j-1])< 0; j--) a[j] = a[j-1]; a[j] = tmp; }}
/** Quicksort algorithm(driver).*/public static void quicksort( Comparable[] a ){ quicksort(a,0,a.length-1);}/** Internal quicksort method that makes recursive calls.* Uses median-of-three partitioning and a cutoff.* 使用三者取中拆分和小数组截断点的快速排序*/private static void quicksort(Comparable[] a , int low, int high){ if(low + CUTOFF > high ) insertionSort(a,low,high);//测试小数组,当问题小于CUTOFF给出特定值时用插 //入排序 else{ //对low, middle, high位置处的元素进行排序,然后将它们放在合适的位置。 int middle = ( low + high )/2; if(a[middle].compareTo(a[low]) < 0 ) swap(a, low, middle);//交换low与middle的值 if(a[high].compareTo(a[low]) < 0 ) swap(a, low, high); if(a[high].compareTo(a[middle]) < 0 ) swap(a, middle, high); swap(a, middle , high-1); Comparable pivot = a[high - 1];//支点的设置 int i,j; for(i=low, j = high-1; ;){ while( a[++i].compareTo( pivot ) < 0 ) ; while( pivot.compareTo( a[--j]) < 0 ) ; if( i >= j) break; swap(a, i , j); } swap(a, i ,high-1);//确定支点的位置 quicksort(a, low, i-1); quicksort(a, i+1, high); }}