75. Sort Colors - LeetCode

Question

75. Sort Colors

Solution

题目大意:

给一个数组排序,这个数组只有0,1,2三个元素,要求只遍历一遍

思路:

记两个索引,lowIdx初始值为0,highIdx初始值为nums.length - 1,遍历数组,如果是2就与highIdx处元素互换且highIdx—,如果是0就与lowIdx处元素互换且lowIdx++,i++,还剩一种情况就是1了,执行i++,循环结束条件是i<=highIdx

Java实现:

public void sortColors(int[] nums) {
    int lowIdx = 0;
    int highIdx = nums.length - 1;
    int i = 0;
    while (i <= highIdx) {
        if (nums[i] == 2) {
            int tmp = nums[highIdx];
            nums[highIdx--] = nums[i];
            nums[i] = tmp;
        } else if (nums[i] == 0) {
            int tmp = nums[lowIdx];
            nums[lowIdx++] = nums[i];
            nums[i++] = tmp;
        } else {
            i++;
        }
    }
}