【leetcode】75. Sort Colors

第一种解法，统计red,white,blue的个数，然后再扫一遍进行置数，two pass

/**
 *  @author         johnsondu
 *  @time           11:26 14th Oct 2015
 *  @status         Accepted
 *  @strategy       two pass
 *  @problem        Set Matrix Zeroes
 *  @url            https://leetcode.com/problems/set-matrix-zeroes/
 */

class Solution {
public:
    void sortColors(vector<int>& nums) {
        int color[3] = {0};
        for(int i = 0; i < nums.size(); i ++)
            color[nums[i]] ++;
        int cnt = 0;
        for(int i = 0; i < 3; i ++){
            int idx = 0;
            while(idx < color[i]) {
                nums[cnt++] = i; 
                idx ++;
            }
        } 
    }
};

第一种解法，利用两个指针，一个指向首个头，

表示red的下标，一个指向数组尾，表示blue的下标。 One pass

</pre></p><pre name="code" class="cpp">/**
 *  @author         johnsondu
 *  @time           11:26 14th Oct 2015
 *  @status         Accepted
 *  @strategy       one pass
 *  @problem        Set Matrix Zeroes
 *  @url            https://leetcode.com/problems/set-matrix-zeroes/
 */

class Solution {
public:
    void sortColors(vector<int>& nums) {
        int ridx = 0;
        int bidx = nums.size() - 1;
        int i = 0;
        while(i < bidx + 1)
        {
            if(nums[i] == 0) {
                swap(nums[i], nums[ridx]);
                ridx ++;
                i ++;
                continue;
            }
            if(nums[i] == 2) {
                swap(nums[i], nums[bidx]);
                bidx --;
                continue;
            }
            i ++;
        }
    } 
};