51Nod 1272最大距离 （树状数组维护前缀最小值）
题目链接 最大距离
其实主流解法应该是单调栈……我用了树状数组。
1 #include <bits/stdc++.h> 2 3 using namespace std; 4 5 #define rep(i, a, b) for (int i(a); i <= (b); ++i) 6 7 const int N = 100010; 8 9 struct node{ 10 int x, y; 11 friend bool operator < (const node &a, const node &b){ 12 return a.x == b.x ? a.y < b.y : a.x < b.x; 13 } 14 //sort细节，初始ID在前的最后也要在前 15 } a[N]; 16 17 int f[N]; 18 int n, ans; 19 20 void update(int x, int val){ 21 for (; x <= n; x += x & -x) f[x] = min(f[x], val); 22 } 23 24 //树状数组更新 25 26 int query(int x){ 27 int ret = 1 << 30; 28 for (; x; x -= x & -x) ret = min(ret, f[x]); 29 return ret; 30 } 31 32 //树状数组查询前缀最小值 33 34 int main(){ 35 36 scanf("%d", &n); 37 rep(i, 1, n){ 38 scanf("%d", &a[i].x); 39 a[i].y = i; 40 } 41 42 sort(a + 1, a + n + 1); 43 rep(i, 0, n + 100) f[i] = 1 << 30; //Init... 44 45 ans = -1; 46 rep(i, 1, n){ 47 update(a[i].y, a[i].y); 48 int cnt = query(a[i].y); 49 ans = max(ans, a[i].y - cnt); 50 } 51 printf("%d\n", ans); 52 return 0; 53 }
