题目
Shuffle a set of numbers without duplicates.
Example:
// Init an array with set 1, 2, and 3. int[] nums = {1,2,3}; Solution solution = new Solution(nums); // Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned. solution.shuffle(); // Resets the array back to its original configuration [1,2,3]. solution.reset(); // Returns the random shuffling of array [1,2,3]. solution.shuffle();
解法
遍历数组,并产生一个随机索引,交换当前元素和随机元素,直到数组结束,就可以达到洗牌的目的。
reset只能保留数组副本。
class Solution {
private int[] array;
private int[] original;
Random random=new Random();
public Solution(int[] nums) {
array=nums;
original=nums.clone();
}
private int randRange(int min,int max){
return random.nextInt(max-min)+min;
}
/** Resets the array to its original configuration and return it. */
public int[] reset() {
array=original;
return original.clone();
}
private void swap(int i, int j) {
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
/** Returns a random shuffling of the array. */
public int[] shuffle() {
for(int i=0;i<array.length;i++){
swap(i,randRange(i,array.length));
}
return array;
}
}
/**
* Your Solution object will be instantiated and called as such:
* Solution obj = new Solution(nums);
* int[] param_1 = obj.reset();
* int[] param_2 = obj.shuffle();
*/