75. Sort Colors

题目：

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.

将相同颜色物体集在一起，并按序排列。

两个指针，分别指向red和blue

public void sortColors(int[] nums) {
int start=0;
int end=nums.length-1;
for(int i=0;i<end+1;i++)
{
if(nums[i]==0)
{
nums[i++]=nums[start];
nums[start++]=0;
}
else if(nums[i]==2)
{
nums[i++]=nums[end];
nums[end--]=2;
}
else
{
i++;
}
}
}分别统计每个物体的个数：
public void sortColors(int[] nums) {
int sum=0;
int count=0;
for(int i=0;i<nums.length;i++)
{
sum+=nums[i];
if(nums[i]==1)count++;
}

int count2 = (sum-count)/2;
int count0 = nums.length-count-count2;
for(int i=0;i<count0;i++)
{
nums[i]=0;
}
for(int i=count0;i<count0+count;i++)
{
nums[i]=1;
}
for(int i=count0+count;i<nums.length;i++)
{
nums[i]=2;
}
}