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.
分析:对0,1,2排序,用3个指针,一个指到最右边,一个指到最左边,一个指当前对象。如果是0往最左边移动,如果是2往最右边移动。移动后对应边界改变。O(N)复杂度。
class Solution {
public:
void sortColors(int A[], int n) { //use three point , point right ,left,and curr
int left = 0;
int right = n-1;
int curr = left;
while(curr<=right){
curr = (curr<=left)?left:curr;
if(A[curr]==0){
swap(A,left++,curr++);
}
else if(A[curr]==2){
swap(A,right--,curr);
}
else{
++curr;
}
}
}
void swap(int A[],int a,int b){
int temp = A[b];
A[b] = A[a];
A[a] = temp;
}
};