英文:
Merge-Sort implementation / suspecting mistake in recursive call or while merging
问题
任何对这个混乱的帮助都会被赞赏。这里的任务是对一个不包含零的整数数组进行排序。我认为我犯了两个错误，但我无法解决。
第一：我认为在递归调用时犯了一个错误。合并时似乎设置了错误的边界。
第二：我也认为排序过程中存在多个错误。
static void mergeSort(int[] init, int lower, int upper) {
if (lower < upper) {
int mid = (lower + upper) / 2;
mergeSort(init, lower, mid);
mergeSort(init, mid+1, upper);
merge(init, lower, mid, upper);
}
}
static void merge(int[] init, int lower, int mid, int upper) {
int length1 = mid - lower; //第一个子数组的长度
int length2 = upper - mid; //第二个子数组的长度
int[] leftArray = new int[length1+1]; //创建左子数组
int[] rightArray = new int[length2+1]; //创建右子数组
for (int i = 0; i < length1; i++) { //将左分区的位置复制到左子数组
leftArray[i] = init[lower + i];
}
for (int i = 0; i < length2; i++) { //将右分区的位置复制到右子数组
rightArray[i] = init[mid+i+1]; //注意这里要加1，因为mid包含在左子数组中
}
int i = 0;
int j = 0;
for (int k = lower; k < upper; k++) {
if (i < length1 && (j >= length2 || leftArray[i] <= rightArray[j])) { //添加了对i和j的边界检查
init[k] = leftArray[i];
i++;
} else {
init[k] = rightArray[j];
j++;
}
}
}
希望这有助于解决你的问题。
英文:
any help with this mess is appreciated. The task here is to sort an array of integers that differ from zero. I think i made two mistakes which i cant manage to solve.
first: i think i made a mistake at the recursive call. The bounds seem to be set the wrong way while merging
second: i also think the sorting process has several errors too
static void mergeSort(int[] init, int lower, int upper) {
if (lower < upper) {
int mid = (lower + upper) / 2;
mergeSort(init, lower, mid);
mergeSort(init, mid+1, upper);
merge(init, lower, mid, upper);
}
}
static void merge(int[] init, int lower, int mid, int upper) {
int length1 = mid - lower; //length of first subarray
int length2 = upper - mid; //length of second subarray
int[] leftArray = new int[length1+1]; //creating left subArray
int[] rightArray = new int[length2+1]; //creating right subArray
for (int i = 0; i < length1; i++) { //copying positions from left partition to left subArray
leftArray[i] = init[lower + i];
}
for (int i = 0; i < length2; i++) { //copying positions from right partition to right subArray
rightArray[i] = init[mid+i];
}
int i = 0; //sorting
int j = 0;
for (int k = lower; k < upper; k++) {
if (leftArray[i] <= rightArray[j]) {
init[k] = leftArray[i];
i++;
} else {
init[k] = rightArray[j];
j++;
}
}
}
答案1
得分: 0
这是使用静态方法逐步执行归并排序的推荐方法吗：
public static void mergeSort(int[] init, int arrayLength) {
if (arrayLength < 2) {
return;
}
int mid = arrayLength / 2;
int[] left = new int[mid];
int[] right = new int[arrayLength - mid];
for (int i = 0; i < mid; i++) {
left[i] = init[i];
}
for (int i = mid; i < arrayLength; i++) {
right[i - mid] = init[i];
}
mergeSort(left, mid);
mergeSort(right, arrayLength - mid);
merge(init, left, right, mid, arrayLength - mid);
}
public static void merge(
int[] init, int[] left, int[] right, int leftLength, int rightLength) {
int i = 0, j = 0, k = 0;
while (i < leftLength && j < rightLength) {
if (left[i] <= right[j]) {
init[k++] = left[i++];
}
else {
init[k++] = right[j++];
}
}
while (i < leftLength) {
init[k++] = left[i++];
}
while (j < rightLength) {
init[k++] = right[j++];
}
}
调用 "mergeSort"，第一个参数是要排序的数组，第二个参数是它的长度。
祝好！
英文:
Wasn't this the recommended way to do the merge sort step-by-step using static methods:
public static void mergeSort(int[] init, int arrayLength) {
if (arrayLength < 2) {
return;
}
int mid = arrayLength / 2;
int[] left = new int[mid];
int[] right = new int[arrayLength - mid];
for (int i = 0; i < mid; i++) {
left[i] = init[i];
}
for (int i = mid; i < arrayLength; i++) {
right[i - mid] = init[i];
}
mergeSort(left, mid);
mergeSort(right, arrayLength - mid);
merge(init, left, right, mid, arrayLength - mid);
}
public static void merge(
int[] init, int[] left, int[] right, int leftLength, int rightLength) {
int i = 0, j = 0, k = 0;
while (i < leftLength && j < rightLength) {
if (left[i] <= right[j]) {
init[k++] = left[i++];
}
else {
init[k++] = right[j++];
}
}
while (i < leftLength) {
init[k++] = left[i++];
}
while (j < rightLength) {
init[k++] = right[j++];
}
}
Call "mergeSort" with the 1st parameter being the array to be sorted and the 2nd parameter being it's length.
Cheers!
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论