第2章 排序 | | 第17节 三色排序练习题

class ThreeColor {
public:

    //思路有bug
    vector<int> sortThreeColor(vector<int> A, int n) {
        // write code here
        int i = 0;
        while (A[i] == 0)
            i++;
        int k = n - 1;
        while (A[k] == 2)
            k--;
        int j = i;
        while (j < k)
        {
            if (A[j] == 0)
            {
                swap(A[i], A[j]);
                while (A[i] == 0)
                    i++;
            }
            else if (A[j] == 2)
            {
                swap(A[j], A[k]);
                while (A[k] == 2)
                    k--;
            }
            else
            {
                j++;
            }
        }
        return A;
    }

    vector<int> sortThreeColor2(vector<int> A, int n) {
        // write code here
        // 利用快排思想
        int left = -1, right = n;
        int index = 0;
        while (index<right)
        {
            if (A[index]==0)
            {
                swap(A[++left],A[index]);
                index++;
            }else if (A[index]==2)
            {
                swap(A[index], A[--right]);
            }
            else
            {
                index++;
            }
        }
        return A;
    }
};

# -*- coding:utf-8 -*-

class ThreeColor:
    def sortThreeColor(self, A, n):
        # write code here
        left=-1
        right=n
        index=0
        while index<right:
            if A[index]==0:
                left+=1
                A[left],A[index]=A[index],A[left]
                index+=1
            elif A[index]==2:
                right-=1
                A[right],A[index]=A[index],A[right]
            else:
                index+=1
        return A