Maximum Product Subarray 最大連續乘積子集

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.

此題要求是要在一個無需的數組找出一個乘積最大的連續子數組

例如[2,3,-2,4]，由於可能有負數，能夠設置兩個臨時變量mint和maxt，mint存儲遇到負數以後相乘變小的乘積，maxt用來存儲大的乘積。

好比2*3=6，此時，mint = maxt = 6,當下次遇到-2時，mint = maxt = -12，此時乘積-12小於-2，則應使maxt = -2。爲避免下個數仍是負數，應使mint不變，若下次遇到負數，則乘積比maxt大，而後交換……

具體看代碼：

 1 public class Solution {
 2     public int maxProduct(int[] A) {
 3         int n = A.length;
 4         int mint = 1;
 5         int maxt = 1;
 6         
 7         int maxvalue = A[0];
 8         for(int i =  0 ; i < n ; i++){
 9             if(A[i] == 0){
10                 mint = 1;
11                 maxt = 1;
12                 if(maxvalue < 0)
13                     maxvalue = 0;
14             }else{
15                 int curmax = maxt * A[i];
16                 int curmin = mint * A[i];
17                 
18                 maxt = curmax > curmin ? curmax : curmin;
19                 mint = curmax > curmin ? curmin : curmax;
20                 
21                 if(maxt < A[i])
22                     maxt = A[i];
23                     
24                 if(mint > A[i])
25                     mint = A[i];
26                     
27                 if(maxt > maxvalue)
28                     maxvalue = maxt;
29             }
30         }
31         
32         return maxvalue;
33         
34     }
35 }