Sort Colors_LeetCode
Description:
Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.
Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.
Note:
You are not suppose to use the library's sort function for this problem.
解题思路:
题目要求把0,1,2分别代表红色,白色,蓝色的一个序列重新排列,同一种颜色(数值相同的元素)排列相邻。
(方法一):简单来看,这题可以看成一个排序题目,我直接用最简单的冒泡排序写的,很弱智的方法。
时间复杂度为O(n^2)。
(方法二):第一次遍历,用三个变量分别存储红色,白色,蓝色的个数。
第二次遍历,重新对数组根据三个变量进行赋值。
时间复杂度有所优化,为O(n^2)。
代码:
/*方法一*/
class Solution { public: void sortColors(vector<int>& nums) { for (int i = 0; i < nums.size(); i++) { for (int j = i+1; j < nums.size(); j++) { if (nums[i]>nums[j]) { int temp; temp = nums[i]; nums[i] = nums[j]; nums[j] = temp; } } } } };
/*方法二*/
class Solution {
public:
void sortColors(vector<int>& nums) {
int red = 0;
int white = 0;
int blue = 0;
for(int i = 0; i < nums.size(); i++) {
if (nums[i] == 0) {
red++;
}
if (nums[i] == 1) {
white++;
}
if (nums[i] == 2) {
blue++;
}
}
int i;
for (i = 0; i < red; i++) {
nums[i] = 0;
}
int j;
for (j = red; j < red+white; j++) {
nums[j] = 1;
}
for (int k = red+white; k < red+white+blue; k++) {
nums[k] = 2;
}
}
};