205B Little Elephant and Sorting

贪心：每次对于比前面的数小的数累加差值即可，比前面大的可以通过加大区间范围保持大小关系不变；

# include <cstdio>

int n, a[100005];

void init(void)
{
    int i;

    scanf("%d", &n);
    for (i = 0; i < n; ++i)
        scanf("%d", &a[i]);
}

void solve(void)
{
    int i;
    long long int ans;

    ans = 0;
    for (i = 1; i < n; ++i) if (a[i] < a[i-1])
        ans += a[i-1]-a[i];
    printf("%I64d\n", ans);
}

int main()
{
    init();
    solve();

    return 0;
}