這裏是合併了歸併的實現,在Java的作品:合併算法
void merge(int[] numbers, int low, int mid, int high) {
int helper[] = new int[numbers.length];
for (int i = low; i <= high; i++) {
helper[i] = numbers[i];
}
int lowone = low;
int lowtwo = mid + 1;
int count = low;
while (lowone <= mid || lowtwo <= high) {
if (lowone <= mid && lowtwo <= high) {
if (helper[lowone] <= helper[lowtwo]) {
numbers[count] = helper[lowone];
lowone++;
} else {
numbers[count] = helper[lowtwo];
lowtwo++;
}
}
else if (lowone <= mid) {
numbers[count] = helper[lowone];
lowone++;
}
else {
numbers[count] = helper[lowtwo];
lowtwo++;
}
count++;
}
}
//msort algorithm in case it's relevant
void msort(int[] arr, int low, int high) {
if (low < high) {
int mid = (low + high)/2;
msort(arr, low, mid);
msort(arr, mid + 1, high);
merge(arr, low, mid, high);
}
}
在我第一次嘗試合併,我想有數組的後半部分包含中點指數,而不是具有它在上半場。這裏是relavent代碼(注意,是從上面只有4個變化):
int lowtwo = mid;
while (lowone < mid || lowtwo <= high) {
if (lowone < mid && lowtwo <= high) {
if (helper[lowone] <= helper[lowtwo]) {
numbers[count] = helper[lowone];
lowone++;
} else {
numbers[count] = helper[lowtwo];
lowtwo++;
}
}
else if (lowone < mid) {
numbers[count] = helper[lowone];
lowone++;
}
else {
numbers[count] = helper[lowtwo];
lowtwo++;
}
與msort(以上)使用修改後的版本不正確列表進行排序。也許這很明顯,但我似乎無法弄清楚爲什麼它不起作用。