Merge pull request #575 from balasbk/master

max subarray sum

Author: probot-auto-merge[bot]

C++/max subarray sum.cpp

@@ -0,0 +1,66 @@
+// A Divide and Conquer based program for maximum subarray sum problem 
+#include <bits/stdc++.h> 
+
+
+// A utility funtion to find maximum of two integers 
+int max(int a, int b) { return (a > b)? a : b; } 
+
+// A utility funtion to find maximum of three integers 
+int max(int a, int b, int c) { return max(max(a, b), c); } 
+
+// Find the maximum possible sum in arr[] auch that arr[m] is part of it 
+int maxCrossingSum(int arr[], int l, int m, int h) 
+{ 
+	// Include elements on left of mid. 
+	int sum = 0; 
+	int left_sum = INT_MIN; 
+	for (int i = m; i >= l; i--) 
+	{ 
+		sum = sum + arr[i]; 
+		if (sum > left_sum) 
+		left_sum = sum; 
+	} 
+
+	// Include elements on right of mid 
+	sum = 0; 
+	int right_sum = INT_MIN; 
+	for (int i = m+1; i <= h; i++) 
+	{ 
+		sum = sum + arr[i]; 
+		if (sum > right_sum) 
+		right_sum = sum; 
+	} 
+
+	// Return sum of elements on left and right of mid 
+	return left_sum + right_sum; 
+} 
+
+// Returns sum of maxium sum subarray in aa[l..h] 
+int maxSubArraySum(int arr[], int l, int h) 
+{ 
+// Base Case: Only one element 
+if (l == h) 
+	return arr[l]; 
+
+// Find middle point 
+int m = (l + h)/2; 
+
+/* Return maximum of following three possible cases 
+	a) Maximum subarray sum in left half 
+	b) Maximum subarray sum in right half 
+	c) Maximum subarray sum such that the subarray crosses the midpoint */
+return max(maxSubArraySum(arr, l, m), 
+			maxSubArraySum(arr, m+1, h), 
+			maxCrossingSum(arr, l, m, h)); 
+} 
+
+/*Driver program to test maxSubArraySum*/
+int main() 
+{ 
+int arr[] = {2, 3, 4, 5, 7}; 
+int n = sizeof(arr)/sizeof(arr[0]); 
+int max_sum = maxSubArraySum(arr, 0, n-1); 
+printf("Maximum contiguous sum is %dn", max_sum); 
+getchar(); 
+return 0; 
+}