HDU 4923

来源：互联网发布：featutelayer json 编辑：程序博客网时间：2024/06/06 00:19
去掉前导0和后导1
之后切分成1111100,11100,10连续的一段，每段算一个平均值合并
#include <cstdio>#include <cstring>#include <stack>using namespace std;const int maxn = 100007;const double eps = 1e-8;int num[maxn];struct Seg {    int l, r, zero, one;};int tot_s;struct Seg s[maxn];stack<struct Seg> sta;int sgn(double x) {    return x < -eps ? -1 : x > eps;}double cal(struct Seg a) {    double ans = a.one + a.zero;    ans = a.one / ans;    return ans;}int main() {//    freopen("in.txt" , "r", stdin);    int n;    int test_case;    scanf("%d", &test_case);    while (test_case--) {        scanf("%d", &n);        double ans = 0;        int loc_first = 0;        int loc_last = n + 1;        tot_s = 0;        for (int i = 1; i <= n; i++) {            scanf("%d", &num[i]);        }        for (int i = 1; i <= n && num[i] == 0; i++) {            loc_first = i;        }        for (int j = n; j >= 1 && num[j] == 1; j--) {            loc_last = j;        }        loc_last--;        loc_first++;        num[n + 1] = 1;        if (loc_first > loc_last) {            printf("%.6f\n", ans);            continue;        }        while (loc_first <= loc_last) {            s[tot_s].l = loc_first;            while (num[loc_first] == 1) {                loc_first++;            }            s[tot_s].one = loc_first - s[tot_s].l;            while (num[loc_first] == 0) {                loc_first++;            }            s[tot_s].r = loc_first - 1;            s[tot_s].zero = s[tot_s].r - s[tot_s].l + 1 - s[tot_s].one;            tot_s++;        }//        for (int i = 0; i < tot_s; i++) {//            printf("%d %d\n", s[i].l, s[i].r);//        }        sta.push(s[0]);        for (int i = 1; i < tot_s; i++) {            struct Seg cnt = s[i];            while (!sta.empty()) {                double pre_ave = cal(sta.top());                double cnt_ave = cal(cnt);                if (sgn(cnt_ave - pre_ave) >= 0) {                    sta.push(cnt);                    break;                }                struct Seg pre_seg = sta.top();                sta.pop();                cnt.l = pre_seg.l;                cnt.one += pre_seg.one;                cnt.zero += pre_seg.zero;            }            if (sta.empty()) {                sta.push(cnt);            }        }        while (!sta.empty()) {            struct Seg cnt = sta.top();            double ave = cal(cnt);            ans += (1 - ave) * (1 - ave) * cnt.one + ave * ave * cnt.zero;            sta.pop();        }        printf("%.6f\n", ans);    }    return 0;}
0 0