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
.
此题要求是要在一个无需的数组找出一个乘积最大的连续子数组
例如[2,3,-2,4],因为可能有负数,可以设置两个临时变量mint和maxt,mint存储遇到负数之后相乘变小的乘积,maxt用来存储大的乘积。
比如2*3=6,此时,mint = maxt = 6,当下次遇到-2时,mint = maxt = -12,此时乘积-12小于-2,则应使maxt = -2。为避免下个数还是负数,应使mint不变,若下次遇到负数,则乘积比maxt大,然后交换……
具体看代码:
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 }