给定一个数组arr,和一个数num,请把小于num的数放在数组的左边,等于num的数放在数组的中间,大于num的数放在数组的右边。相当于快排的partition过程
public class Flag {
public static int[] flag(int[] arr, int l, int r, int p) {
int less = l - 1;
int more = r + 1;
while (l < more) {
if (arr[l] < p) {
swap(arr, ++less, l++);
} else if (arr[l] > p) {
swap(arr, --more, l);
} else {
l++;
}
}
return new int[]{ less + 1, more - 1 };
}
public static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
public static void printArray(int[] arr) {
for (int i=0; i<arr.length; ++i) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static int[] generateArray() {
int[] arr = new int[10];
for (int i=0; i < arr.length; ++i) {
arr[i] = (int) (Math.random() * 3);
}
return arr;
}
public static void main(String[] args) {
int[] arr = generateArray();
printArray(arr);
int[] res = flag(arr,0, arr.length-1,1 );
printArray(arr);
System.out.println(res[0]);
System.out.println(res[1]);
}
}