In fact, this is to investigate high efficiency, solve the problem of conflict
Take 100 as an example. When 1000W is used, you can change the value. When 1-100 is convenient, the output check is correct.
Build an array of value sizes and store values in the 1-value range by subscript.
Once you have such an array, use random.nextint (value) to randomly generate values in the range [0,value] each time, swap count+value with count+value as the subscript for two numbers at count+value and position count. For example, swap list[0+5] with list[0]. Next count++, swap a position with list[1], which is equivalent to randomly selecting the 0th position and the first position of the array. Count +value cannot exceed the value of the original value.
public static void main(String[] args) {
Random random = new Random();
long start = System.currentTimeMillis();
int value = 100;
// Using arrays is faster
int[] list = new int[value];
for (int j = 0; j < value; ++j) {
list[j] = j+1;
}
int index = 0;
int count = 0;
int tmp = 0;
while (value > 0) {
index = random.nextInt(value);
//System.out.println(list[count + index]);
tmp = list[count + index];
list[count + index] = list[count];
list[count] = tmp;
++count;
–value;
}
long end = System.currentTimeMillis();
//—- Verify that the information is correct
Arrays.sort(list);
int i = 0, size = list.length;
for (; i < size; ++i) {
//System.out.println(list[i]);
if (list[i] ! = (i + 1))
System.out.println(i + “error” + list[i]);
}
//—- Verify that the information is correct
System.out.println(“creat4——“);
System.out.println(” execution time: “+ (end-start) / 1000f +” seconds “);
System.out.println(” end, set size + list.length “);
}
Actual test results:
creat3——
Execution time: 5.169 seconds
That’s it. The set size is 10000000
creat4——
Execution time: 0.729 seconds
That’s it. The set size is 10000000
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