LeetCode——Move Zeroes

LeetCode——Move Zeroes

Question

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:

You must do this in-place without making a copy of the array.

Minimize the total number of operations.

Solution

用两个指针，第一个指针找到第一个为0的位置i，然后另外一个指针从i+1开始找第一个不为0的位置j。然后交换两个数字即可，时间复杂度O(n)

Answer

class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int i = 0;
        int j;

        while (1) {
            int flag = 1;
            int flag2 = 1;
            while (i < nums.size()) {
                if (nums[i] != 0)
                    i++;
                else {
                    flag = 0;
                    break;
                }
            }
            j = i + 1;
            while (j < nums.size()) {
                if (nums[j] == 0)
                    j++;
                else {
                    flag2 = 0;
                    break;
                }
            }
            if (flag == 1 || flag2 == 1)
                break;
            else {
                int tmp;
                tmp = nums[i];
                nums[i] = nums[j];
                nums[j] = tmp;
            }
        }

        for (int i = 0; i < nums.size(); i++)
            cout << nums[i] << endl;
    }
};

网上给出了一种更简单的写法

class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int j = 0;
        // move all the nonzero elements advance
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] != 0) {
                nums[j++] = nums[i];
            }
        }
        for (;j < nums.size(); j++) {
            nums[j] = 0;
        }
    }
};