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maximumSubArray.cpp
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73 lines (64 loc) · 1.67 KB
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// Source : https://oj.leetcode.com/problems/maximum-subarray/
// Author : Hao Chen
// Date : 2014-06-20
/**********************************************************************************
*
* Find the contiguous subarray within an array (containing at least one number)
* which has the largest sum.
*
* For example, given the array [−2,1,−3,4,−1,2,1,−5,4],
* the contiguous subarray [4,−1,2,1] has the largest sum = 6.
*
* More practice:
*
* If you have figured out the O(n) solution, try coding another solution using
* the divide and conquer approach, which is more subtle.
*
*
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define INT_MIN (-2147483647 - 1)
int maxSubArray1(int A[], int n);
int maxSubArray2(int A[], int n);
int max(int x, int y){
return x>y?x:y;
}
int maxSubArray(int A[], int n) {
if (random()%2){
return maxSubArray1(A, n);
}
return maxSubArray2(A, n);
}
int maxSubArray1(int A[], int n) {
int *sum = new int[n];
sum[0] = A[0];
int m = A[0];
for (int i=1; i<n; i++){
sum[i] = max(A[i], A[i] + sum[i-1]);
m = max(m, sum[i]);
}
delete[] sum;
return m;
}
int maxSubArray2(int A[], int n) {
int m=INT_MIN;
int sum=0;
for (int i=0; i<n; i++){
sum += A[i];
m = max(sum, m);
if (sum<0){
sum = 0;
}
}
return m;
}
int main()
{
srand(time(NULL));
int a[]= {-2,1,-3,4,-1,2,1,-5,4};
printf("%d\n", maxSubArray(a, sizeof(a)/sizeof(int)));
printf("%d\n", maxSubArray(a, sizeof(a)/sizeof(int)));
return 0;
}