LeetCode Maximum Product Subarray
来源:程序员人生 发布时间:2014-12-14 08:40:15 阅读次数:2081次
Find the contiguous subarray within an array (containing at least one number) which has the largest product.
For example, given the array [2,3,⑵,4]
,
the contiguous subarray [2,3]
has the largest product = 6
.
思路分析:这题与LeetCode Maximum Subarray类似,只是要注意两个负数的乘积可能变成1个很大的正数,因此要同时保护maxLocal和minLocal和maxGlobal,初值为A[0],以后从A[1]开始遍历,maxLocal取A[i],A[i]*maxLocal.A[i]*minLocal中的最大,minLocal取A[i],A[i]*maxLocal.A[i]*minLocal中的最小,maxGlobal则是始终保存maxLocal中的最大值。要注意,更新minLocal时要用到原始的maxLocal的拷贝,而不是更新以后的值。
AC Code:
public class Solution {
public int maxProduct(int[] A) {
//01:42
if(A.length == 0) return 0;
if(A.length == 1) return A[0];
int maxLocal = A[0];
int minLocal = A[0];
int maxGlobal = A[0];
for(int i = 1; i < A.length; i++){
int maxCopy = maxLocal;
maxLocal = Math.max(Math.max(A[i], A[i] * maxLocal), A[i] * minLocal);
minLocal = Math.min(Math.min(A[i], A[i] * maxCopy), A[i] * minLocal);
maxGlobal = Math.max(maxGlobal, maxLocal);
}
return maxGlobal;
//01:47
}
}
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