程序员面试题：排序和查找的实现（JAVA版）

1、排序

class Sort {//选择排序void selectionsort(int array[], int low, int high){for(int i = low; i <= high-1; i++){for(int j = i+1; j <=high; j++){if(array[i] > array[j]){int temp = array[i];array[i] = array[j];array[j] = temp;}}}}//冒泡排序void bubblesort(int array[],int length){for(int i = 0; i <= length-1; i++){for(int j = 0; j <= length-i-1; j++){if(array[j] > array[j+1]){int temp = array[j+1];array[j+1] = array[j];array[j] = temp;}}}}//归并排序void mergesort(int array[], int low, int high){if(low < high){int middle = (low + high)/2;mergesort(array, low, middle);mergesort(array, middle+1, high);merge(array, low, middle, high);}}void merge(int array[], int low, int mid, int high){int helper[] = new int[array.length];for(int i = low; i < high; i++){helper[i] = array[i];}int current = low;int helperLeft = low;int helperRight = mid+1;while(helperLeft <= mid && helperRight <= high){if(helper[helperLeft] <= helper[helperRight]){array[current++] = helper[helperLeft++];}else{array[current++] = helper[helperRight++];}}int remain = mid - helperLeft;for(int i = 0; i <= remain; i++){array[current + i] = helper[helperLeft+i];}}//快速排序void quicksort(int array[], int left, int right){int index = partition(array, left, right);if(left < index-1){quicksort(array, left, index-1);}else{quicksort(array, index, right);}}int partition(int array[], int left, int right){int piovt = array[(left+right)/2];while(left < right){while(array[left] < piovt) left++;while(array[right] > piovt) right--;    if(left <= right){    int temp = array[left];    array[left] = array[right];    array[right] = temp;    left++;    right--;    }}return left;}}

2、查找

class Search {int binarySearch(int a[], int x){int low = 0;int high = a.length - 1;int mid;while(low <= high){mid = (low + high)/2;if(a[mid] > x){low = mid + 1;}else if(a[mid] < x){high = mid - 1;}else{return mid;}}return -1;}}