codeforces 659C . Tanya and Toys 二分

题目链接

将给出的已经有了的排序， 在前面加上0， 后面加上1e9+1。

然后对相邻的两项判断。 如果相邻两项之间的数的和小于m， 那么全都选上， m减去相应的值。

如果大于m， 那么二分判断最多能选多少个。

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <complex>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef complex <double> cmx;
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
const int maxn = 1e5+5;
int ans[maxn], a[maxn], cnt;
int check(int l, int r, int sum) {
    int len = r-l+1;
    ll tmp = 1LL*(l+r)*len/2;
    if(tmp<=sum)
        return 1;
    return 0;
}
void bin(int l, int r, int sum) {
    int pos = l;
    int tmpl = l;
    while(l<=r) {
        int m = l+r>>1;
        if(check(tmpl, m, sum)) {
            pos = m;
            l = m+1;
        } else
            r = m-1;
    }
    for(int i = tmpl; i <= pos; i++)
        ans[cnt++] = i;
}
int main()
{
    int n, m;
    cin>>n>>m;
    a[0] = 0;
    for(int i = 1; i <= n; i++)
        scanf("%d", &a[i]);
    a[++n] = 1e9+1;
    sort(a, a+n+1);
    for(int i = 0; i < n; i++) {
        int tmp = a[i+1]-a[i];
        if(tmp==1)
            continue;
        if(tmp==2) {
            if(m>=a[i]+1) {
                m -= (a[i]+1);
                ans[cnt++] = a[i]+1;
                continue;
            } else
                break;
        }
        int a1 = a[i]+1, an = a[i+1]-1;
        tmp--;
        ll sum = 1LL*(a1+an)*tmp/2;
        if(sum<=m) {
            m -= sum;
            for(int j = a[i]+1; j<=a[i+1]-1; j++) {
                ans[cnt++] = j;
            }
        } else {
            if(a1<=m) {
                bin(a1, an, m);

            }
            break;
        }
    }
    cout<<cnt<<endl;
    for(int i = 0; i < cnt; i++)
        printf("%d ", ans[i]);
    return 0;
}