max sum of subarray

DynamicPrograms/maxSubArray.go

@@ -0,0 +1,59 @@
+/*
+53. Maximum Subarray
+
+Given an integer array nums, find the subarray
+which has the largest sum and return its sum.
+
+Example 1:
+
+Input: nums = [-2,1,-3,4,-1,2,1,-5,4]
+Output: 6
+Explanation: [4,-1,2,1] has the largest sum = 6.
+Example 2:
+
+Input: nums = [1]
+Output: 1
+Example 3:
+
+Input: nums = [5,4,-1,7,8]
+Output: 23
+*/
+
+// solution:
+/*
+	1. Find the currSum at every index, by adding curSum and current value.
+	2. If currSum > maxSum:
+		maxSum = curSum
+	3. if currSum < 0, means, adding current value is not meaningful, then make
+		curSum = 0, and proceed for next element
+*/
+
+package main
+
+import "fmt"
+
+func maxSubArray(nums []int) int {
+	n := len(nums)
+	maxSum := nums[0]
+	currSum := 0
+	for i := 0; i < n; i++ {
+		currSum = currSum + nums[i]
+
+		if currSum > maxSum {
+			maxSum = currSum
+		}
+
+		if currSum < 0 {
+			currSum = 0
+		}
+	}
+	return maxSum
+}
+
+func main() {
+	nums := []int{-2, 1, -3, 4, -1, 2, 1, -5, 4}
+	fmt.Println("max subarray sum:", maxSubArray(nums))
+}
+
+// output:
+// max subarray sum: 6