常用的排序
不知不觉都过了一年了,只能感叹时光易逝啊。
10号要去软件园那边应聘实习生,所以今天晚上抽点时间复习了一遍常用的排序。
一. 冒泡
void MaoPao(int *nums, int length) { for (int i = length-2; i > 0; i--) { for (int j = 0; j <= i; j++) { if (nums[j + 1] < nums[j]) { swap(&nums[j], &nums[j+1]); } } } }
这是最基础也是最容易想到的排序之一。时间(n²),没啥好说的。
二. 选择
void XuanZhe(int *nums, int length) { int minIndex = 0; bool changed = false; for (int i = 0; i < length-1; i++) { changed = false; minIndex = i; for (int j = i; j < length; j++) { if (nums[j] < nums[minIndex]) { minIndex = j; changed = true; } } if (changed) { swap(&nums[i], &nums[minIndex]); } } }
在冒泡、选择、插入里,选择排序算不错的了,起码对内存的操作没有其他两个那么频繁。
三. 插入
void ChaRu(int *nums, int length) { for (int i = 1; i < length; i++) { for (int j = 0; j < i; j++) { if (nums[i] < nums[j]) { int temp = nums[i]; for (int k = i; k > j; k--) nums[k] = nums[k - 1]; nums[j] = temp; } } } }
插入排序的代码让我想起了大一学C语言的灰暗时光。。。
四. 快排
void KuaiPai_DieDai(int *nums, int start, int end) { if (start >= end) return; int high = end; int low = start; while (low < high) { while(nums[high] >= nums[low]&& low < high) high--; if(low < high) swap(&nums[low], &nums[high]); while (nums[low] <= nums[high] && low < high) low++; if (low < high) swap(&nums[low], &nums[high]); } KuaiPai_DieDai(nums, start, low-1); KuaiPai_DieDai(nums, high+1, end); }
快排就舒服多了。除了不少的low<high有碍观瞻,不管是复杂度还是代码都算很不错的。
五.归并
void GuiBing_DieDai(int *nums, int start, int end, int* temp) { if (start >= end) return; int mid = (start + end) / 2; GuiBing_DieDai(nums, start, mid, temp); GuiBing_DieDai(nums, mid + 1, end, temp); int first_low = start; int first_high = mid; int second_low = mid+1; int second_high = end; int tempIndex = 0; while (first_low <= first_high && second_low <= second_high) { if (nums[first_low] < nums[second_low] ) { temp[tempIndex++] = nums[first_low]; first_low++; } else { temp[tempIndex++] = nums[second_low]; second_low++; } } while (first_low <= first_high) { temp[tempIndex++] = nums[first_low]; first_low++; } while (second_low <= second_high) { temp[tempIndex++] = nums[second_low]; second_low++; } for (int i = 0; i < tempIndex; i++) { nums[start + i] = temp[i]; } }
归并看起来就不那么舒服了,特别是空间上,除了递归的开销还要加个n。不过好在它是稳定的。
六.堆排序
void HeapAdjust(int *nums, int i, int length) { int max = i; int lchild = i * 2 + 1; int rchild = i * 2 + 2; if (lchild < length && nums[lchild] > nums[max]) { max = lchild; } if (rchild < length && nums[rchild] > nums[max]) { max = rchild; } if (max != i) { int temp; temp = nums[i]; nums[i] = nums[max]; nums[max] = temp; HeapAdjust(nums, max, length); } } void Dui(int *nums, int length) { for (int i = length / 2 - 1; i >= 0; i--) { HeapAdjust(nums, i, length); } for (int i = length - 1; i >= 0; i--) { swap(&nums[i], &nums[0]); HeapAdjust(nums, 0, i); } }
第一个for循环构建大顶堆,第二个for循环开始排序。
找实习好难啊。。。