SDUT - 3664 顺序表应用7：最大子段和之分治递归法

#include <stdio.h>
#include <stdlib.h>
int *a, cou = 0;
int max(int a, int b){if(a > b)return a; else return b; }
void creat(int n)
{
    a = (int *)malloc((n + 5) * sizeof(n));
}
void get(int n)
{
    for(int i = 1; i <= n; i++)scanf("%d", &a[i]);
}
int maxsum(int l, int r)
{
    cou++;
    if(l == r)return a[l];
    int mid = (l + r) / 2;
    int sum1 = 0, ans1 = 0, sum2 = 0, ans2 = 0, ans = 0;
    for(int i = mid + 1; i <= r; i++)
    {
        sum1 += a[i];
        ans1 = max(ans1, sum1);
    }
    for(int i = mid - 1; i >= l; i--)
    {
        sum2 += a[i];
        ans2 = max(ans2, sum2);
    }
    ans = max(ans, a[mid] + ans1 + ans2);
    ans = max(ans, maxsum(l, mid));
    ans = max(ans, maxsum(mid + 1, r));
    return ans;
}
int main()
{
    int n, ans;
    scanf("%d", &n);
    creat(n);
    get(n);
    ans = maxsum(1, n);
    printf("%d %d\n", ans, cou);
    return 0;
}