集計ソートMerge Sort
4333 ワード
自分で書いたコードを記録してください
public class MergeSort {
// recursive
public static void mergeSort(int[] nums, int start, int end) {
if(start >= end) {
return;
}
int mid = (start + end) / 2;
mergeSort(nums, start, mid);
mergeSort(nums, mid + 1, end);
merge(nums, start, mid, end);
}
public static void merge(int[] nums, int start, int mid, int end) {
int[] temp = new int[end - start + 1];
int i = start, j = mid + 1, k = 0;
while(i <= mid && j <= end) {
if(nums[i] <= nums[j]) {
temp[k++] = nums[i++];
} else {
temp[k++] = nums[j++];
}
}
while(i <= mid) {
temp[k++] = nums[i++];
}
while(j <= end) {
temp[k++] = nums[j++];
}
i = start;
while(i <= end) {
nums[i] = temp[i - start];
i++;
}
}
// itervative
public static void mergeSort(int[] nums) {
for(int gap = 1; gap < nums.length; gap *= 2) {
for(int start = 0; start < nums.length; start += gap * 2) {
merge(nums, start, Math.min(start + gap - 1, nums.length - 1), Math.min(start + gap * 2 - 1, nums.length - 1));
}
}
}
public static void main(String[] args) {
int[] nums = new int[]{13, 6, 9, 1, 19, -21, 5};
mergeSort(nums);
System.out.println(nums);
}
}