[LeetCode] Maximum Product Subarray

Find the contiguous subarray within an array (containing at least one number) which has the largest product.

For example, given the array [2,3,-2,4],
the contiguous subarray [2,3] has the largest product = 6.

 

class Solution {
public:
    int maxProduct(int A[], int n) {
        int res = A[0];
        int tmp_max = A[0], tmp_min = A[0];
        for (int i = 1; i < n; ++i) {
            int cpy_max = tmp_max;
            tmp_max = max(max(tmp_max * A[i], A[i]), tmp_min * A[i]);
            tmp_min = min(min(cpy_max * A[i], A[i]), tmp_min * A[i]);
            res = max(res, tmp_max);
        }
        return res;
    }
};

有一点要注意。每次循环要备份一下tmp_max，因为经过了对tmp_max的操作，tmp_max的值已经改变了，所以要使用cpy_max来保存改变之前的tmp_max的值。