Submission #42977

#	Time	Username	Problem	Language	Result	Execution time	Memory
42977		BThero	Three Friends (BOI14_friends)	C++14	100 / 100	96 ms	6572 KiB

friends

#include <bits/stdc++.h>

#define pb push_back
#define mp make_pair

#define fi first
#define se second

typedef long long ll;

using namespace std;

char ans[2000005];

char t[2000005];

char s[2000005];

int n;

void solve() {
    scanf("%d", &n);
    scanf("%s", s);

    if (n % 2 == 0) {
        printf("NOT POSSIBLE\n");
        return;
    }

    int len = (n - 1) / 2;

    vector <int> vv;

    {
        int l = 0, r = len + 1;
        int ps = -1;

        for (int i = 1; i <= len; ++i) {
            while (s[l] != s[r]) {
                if (ps == -1) {
                    ps = l;
                }
                else {
                    ps = -2;
                    break;
                }

                ++l;
            }

            if (ps == -2) {
                break;
            }

            ++l, ++r;
        }

        if (ps == -1) {
            ps = len;
        }

        if (0 <= ps) {
            vv.pb(ps);
        }
    }

    {
        int l = 0, r = len;
        int ps = -1;

        for (int i = 1; i <= len; ++i) {
            while (s[l] != s[r]) {
                if (ps == -1) {
                    ps = r;
                }
                else {
                    ps = -2;
                    break;
                }

                ++r;
            }

            if (ps == -2) {
                break;
            }

            ++l, ++r;
        }

        if (ps == -1) {
            ps = n - 1;
        }

        if (0 <= ps) {
            vv.pb(ps);
        }
    }

    bool ex = 0;

    for (auto it : vv) {
        int sz = 0;

        for (int i = 0; i < n; ++i) {
            if (i != it) {
                t[sz++] = s[i];
            }
        }

        bool ok = 1;

        for (int i = 0; i < len; ++i) {
            ok &= (t[i] == t[i + len]);
        }

        if (!ok) {
            continue;
        }

        if (ex) {
            for (int i = 0; i < len; ++i) {
                if (t[i] != ans[i]) {
                    printf("NOT UNIQUE\n");
                    return;
                }
            }
        }

        ex = 1;

        for (int i = 0; i < len; ++i) {
            ans[i] = t[i];
        }
    }

    if (!ex) {
        printf("NOT POSSIBLE\n");
        return;
    }

    for (int i = 0; i < len; ++i) {
        printf("%c", ans[i]);
    }
}

int main() {
    #ifdef BThero
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif // BThero

    int tt = 1;

    while (tt--) {
        solve();
    }

    return 0;
}

Compilation message (stderr)

friends.cpp: In function 'void solve()':
friends.cpp:22:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
                    ^
friends.cpp:23:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s", s);
                   ^

• Subtask 1: 35 / 35
• Subtask 2: 65 / 65