feat(#152): solve the problem #152.Maximum Product Subarray

Author: geemo

152.Maximum Product Subarray/README.md

@@ -0,0 +1,60 @@
+Given an integer array nums, find the contiguous subarray within an array (containing at least one number) which has the largest product.
+
+**Example 1:**
+```
+Input: [2,3,-2,4]
+Output: 6
+Explanation: [2,3] has the largest product 6.
+```
+**Example 2:**
+```
+Input: [-2,0,-1]
+Output: 0
+Explanation: The result cannot be 2, because [-2,-1] is not a subarray.
+```
+
+**Solution:**
+
+```golang
+func maxProduct(nums []int) int {
+  n := len(nums)
+  if n == 1 {
+    return nums[0]
+  }
+
+  dp := make([][2]int, n)
+  if nums[0] < 0 {
+    dp[0][1] = nums[0]
+  } else {
+    dp[0][0] = nums[0]
+  }
+
+  var ans int = dp[0][0]
+  for i := 1; i < n; i++ {
+    if nums[i] > 0 {
+      dp[i][0] = max(dp[i-1][0] * nums[i], nums[i])
+      dp[i][1] = min(dp[i-1][1] * nums[i], nums[i])
+    } else {
+      dp[i][1] = min(dp[i-1][0] * nums[i], nums[i])
+      dp[i][0] = max(dp[i-1][1] * nums[i], nums[i])
+    }
+    ans = max(ans, dp[i][0])
+  }
+
+  return ans
+}
+
+func max(a, b int) int {
+  if a > b {
+    return a
+  }
+  return b
+}
+
+func min(a, b int) int {
+  if a < b {
+    return a
+  }
+  return b
+}
+```