53. Maximum Subarray

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

A subarray is a contiguous part of an array.

 

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

 

Constraints:

• 1 <= nums.length <= 105
• -104 <= nums[i] <= 104

 

Follow up: If you have figured out the O(n) solution, try coding another solution using the divide and conquer approach, which is more subtle.

Normal Solution:

* ㅋㅋ INT_MIN 처음봄......... O-<-<......

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

int maxSubArray(int *nums, int numsSize) {
    int max = INT_MIN;
    int sum = 0;

    for(int i = 0 ; i < numsSize; i++) {
        if( sum >= 0)
            sum += nums[i];
        else
            sum = nums[i];
        
        if(sum > max)
            max = sum;
    }   
    return max;
}   



int main() {
    int a[40] = {-2,1,-3,4, -1, 2, 1, -5, 4};
    
    printf("%d", maxSubArray(a, 9));
    return 0;
}

Divide and Conquer :