java排序
1. 冒泡排序 比较相邻的元素。如果第一个比第二个大,就交换他们两个。
//冒泡排序 public static void bubble(int[] ints) { for(int i = 0; i < ints.length - 1; i++) { for(int j = i + 1; j < ints.length - 1 - i; j++) { if(ints[j] > ints[j + 1]) { ints[i] = ints[i] + ints[j]; ints[j] = ints[i] - ints[j]; ints[i] = ints[i] - ints[j]; } } } }
2. 快速排序
//快速排序 public static void quickSort(int[] ints, int leftIndex, int rightIndex) { //数字的左下标大于等于右下标,中止,递归出口 if(leftIndex >= rightIndex) return; //排序的范围,下一次递归要用,所以复制一份 int left= leftIndex; int right = rightIndex; //基准值,大于基准值的排右边,小于基准值的排左边。如: 5, 3, 1。基准值为3,排序后 1, 3, 5 int midIndex = (leftIndex + rightIndex) / 2; int midValue = ints[midIndex]; while(leftIndex <= rightIndex) { //从左往右找,直至找到大于或等于基准值, <= 会下标越界 while(ints[leftIndex] < midValue) leftIndex++; //在右往左找,直至找到小于或等于基准值, >= 会下标越界 while(ints[rightIndex] > midValue) rightIndex--; if(leftIndex > rightIndex) break; if(leftIndex < rightIndex) {//左右互换位置 ints[leftIndex] = ints[leftIndex] + ints[rightIndex]; ints[rightIndex] = ints[leftIndex] - ints[rightIndex]; ints[leftIndex] = ints[leftIndex] - ints[rightIndex]; } leftIndex++; rightIndex--; } //递归 quickSort(ints, leftIndex, right); quickSort(ints, left, rightIndex); }
3. 选择排序
//选择排序:找到数组中最大的元素,与数组最后一位元素交换 public static void selectSort(int[] ints) { for(int i = 0; i < ints.length - 1; i++) { int maxIndex = 0;//初始化最大值的下标 for(int j = 1; j < ints.length - i; j++) { if(ints[j] > ints[maxIndex]) maxIndex = j; } int lastIndex = ints.length - 1 - i; //未排序中的最后的下标 if(maxIndex != lastIndex) { ints[lastIndex] = ints[lastIndex] + ints[maxIndex]; ints[maxIndex] = ints[lastIndex] - ints[maxIndex]; ints[lastIndex] = ints[lastIndex] - ints[maxIndex]; } } }