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  • 第4章 分治策略 monge阵列

    /* fi表示第i行的最左最小元素的列小标,则有f0<f1<f2<...<fn-1
      取数组的偶数行,组成新的子数组,递归求解最左最小元素的列下表,利用偶数项限定奇数项的范围,再求奇数项
    */
    #include<iostream>
    #include<vector>
    using namespace std;
    void findOddMin(vector<vector<int>> &a, int m, int n, vector<int> &r)
    {
    	int len = r.size();
    	vector<int> tmp;
    	for (int i = 0; i < m; ++i){
    		int b = 0, e = n - 1;
    		if (i % 2 == 0){
    			if (i / 2>0) b = r[i / 2 - 1];
    			if (i / 2 < len) e = r[i / 2];
    			int k = b;
    			for (int j = b + 1; j <= e; ++j)
    				if (a[i][j] < a[i][k]) k = j;
    			tmp.push_back(k);
    		}
    		else tmp.push_back(r[i / 2]);
    	}
    	r = tmp;
    }
    void findMin(vector<vector<int>> &a, int m, int n, vector<int> &r)
    {
    	if (m == 1){
    		int k = 0;
    		for (int i = 1; i < n; ++i)
    			if (a[0][i] < a[0][k]) k = i;
    		r.push_back(k);
    		return;
    	}
    	vector<vector<int>> b;
    	for (int i = 0; i < m; ++i)
    		if (i % 2 == 1) b.push_back(a[i]);
    	findMin(b, m / 2, n, r);
    	findOddMin(a, m, n, r);
    }
    
    int main()
    {
    	//vector<vector<int>> a = { { 10, 13, 23 }, { 17, 16, 23 }, { 45, 32, 23 } };
    	vector<vector<int>> a = { { 37, 23, 22, 32 }, { 21, 6, 5, 10 }, { 53, 34, 30, 31 }, { 32, 13, 9, 6 }, { 43, 21, 15, 8 } };
    	vector<int> r;
    	findMin(a, 5,4, r);
    	for (auto i : r)
    		cout << i << ' ';
    	cout << endl;
    }
    

      

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  • 原文地址:https://www.cnblogs.com/jokoz/p/4693042.html
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