题目链接:http://codeforces.com/problemset/problem/1251/D
给你n个区间,让你从中选出n个数使得,总和加起来不超过m并且中位数最大,求最大的中位数。
当时我自作聪明,判断写在清空的上面写凉了,还是不够精细。
ac代码:
#include<set>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cstring>
#include <iostream>
using namespace std;
typedef long long ll;
const ll inf=0x3f3f3f3f;
const ll mx=4e5+10;
const ll mod=1e9+7;
struct node {
ll a, b;
bool operator<(const node &t) const {
return a>t.a;
}
}s[mx];
ll q, n, m;
bool cmp(ll a) {
ll sum = 0, ts = n/2+1;
for (int i = 0; i < n; ++i) {
if (s[i].b < a || !ts) {
sum += s[i].a;
continue;
}
sum += max(s[i].a, a);
ts--;
}
if (ts) return false;
if (sum <= m) return true;
return false;
}
void solve() {
ll l = 0, r = m, ans = 0;
while (l <= r) {
ll mid = (l+r)>>1;
if (cmp(mid)) {
ans = mid;
l = mid+1;
}
else r = mid-1;
}
printf("%lld\n", ans);
return;
}
int main()
{
scanf("%lld", &q);
for (int i = 0; i < q; ++i) {
scanf("%lld%lld", &n, &m);
for (int j = 0; j < n; ++j)
scanf("%lld%lld", &s[j].a, &s[j].b);
sort(s, s+n);
solve();
}
return 0;
}
wa的代码:
#include<set>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cstring>
#include <iostream>
using namespace std;
typedef long long ll;
const ll inf=0x3f3f3f3f;
const ll mx=4e5+10;
const ll mod=1e9+7;
struct node {
ll a, b;
bool operator<(const node &t) const {
return a>t.a;
}
}s[mx];
ll q, n, m;
bool vis[mx];
bool cmp(ll a) {
ll sum = 0, ts = 0;
for (int i = 0; i < n; ++i) {
if (s[i].b < a) continue;
sum += max(s[i].a, a);
vis[i] = true;
ts++;
if (n/2+1 == ts) break;
}
if (ts != n/2+1) return false;///就是这里写在下面for的下面就行
for (int i = 0; i < n; ++i) {
if(vis[i]) {
vis[i] = 0;
continue;
}
sum += s[i].a;
}
if (sum <= m) return true;
return false;
}
void solve() {
ll l = 0, r = m, ans = 0;
while (l <= r) {
ll mid = (l+r)>>1;
if (cmp(mid)) {
ans = mid;
l = mid+1;
}
else r = mid-1;
}
printf("%lld\n", ans);
return;
}
int main()
{
scanf("%lld", &q);
for (int i = 0; i < q; ++i) {
scanf("%lld%lld", &n, &m);
for (int j = 0; j < n; ++j)
scanf("%lld%lld", &s[j].a, &s[j].b);
sort(s, s+n);
solve();
}
return 0;
}