Arrays.copyOfRange(int[] arr,int开始下标,int结束下标)//左闭右开
System.arraycopy(int[] source,int开始下标,int[] dest,int开始下标,int拷贝多少个)
这里是手动拷贝:
public static int[] copyOf(int[] original, int newLength) {
int[] dest = new int[newLength];
int length = original.length <= newLength ? original.length : newLength;
for (int i = 0; i < length; i++) {
dest[i] = original[i];
}
return dest;
}
mid作为分水岭, 不断地缩小范围
// 前提需要数组是有序的
public static int binarySearch(int[] a, int v) {
int left = 0;
int right = a.length;
while (left < right) {
int mid = (left + right) / 2;
if (v == a[mid]) {
return mid;
} else if (v < a[mid]) {
right = mid;
} else {
left = mid + 1;
}
}
return -1;
}
public static int binarySearch3(int[] a, int v) {
int left = 0;
int right = a.length - 1;
while (left <= right) {
int mid = (left + right) / 2;
if (v == a[mid]) {
return mid;
} else if (v < a[mid]) {
right = mid - 1;
} else {
left = mid + 1;
}
}
return -1;
}
名称栏目:数组拷贝,二分法查找
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