CSP认证练习题目推荐(4)

思维、贪心、综合

排队打水

这道题目不算难，但是不注意还是会出现很多错误，比如结构体的书写。以及自定义结构体排序。还有这里做的优化，使用前缀和记录打水的等待时间，但是这里很容易出错的点在于等待时间是应该是记录的前一个人的前缀和。因为它不需要等待自己打水的等待时间。

#include<bits/stdc++.h>
using namespace std;
int n;
struct node{int index;int t;
}a[1010];
int s[1010];
bool cmp(node a, node b){return  a.t < b.t;
}
int main(){ios::sync_with_stdio(0);cin.tie(0);cin >> n;for(int i = 1; i <= n; i++){cin >> a[i].t;a[i].index = i;}sort(a + 1, a + n + 1, cmp);double ans = 0;for(int i = 1; i <= n; i++){s[i] += s[i - 1] + a[i].t; //构建前缀和数组ans += s[i - 1];cout << a[i].index << " ";}cout << endl;ans /= n;cout << fixed << setprecision(2) << ans;return 0;
}

合并果子

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
int n;
int main(){ios::sync_with_stdio(0);cin.tie(0);cin >> n;priority_queue<ll, vector<ll>, greater<>> q;for(int i = 0; i < n; i++){int num;cin >> num;q.push(num);}ll ans = 0;while(q.size() >= 2){ll a = q.top(); q.pop();ll b = q.top(); q.pop();ans += a + b;q.push(a + b);}cout << ans;return 0;
}

平均分配

#include<bits/stdc++.h>
using namespace std;
using ll = long long;
struct node{ll b;ll c;ll diff;
}pr[200001];
bool cmp(node f, node l){return f.diff > l.diff;
}
int main(){ios::sync_with_stdio(0);cin.tie(0);int n;cin >> n;for(int i = 1; i <= 2*n; i++){cin >> pr[i].b;}for(int i = 1; i <= 2*n; i++){cin >> pr[i].c;pr[i].diff = pr[i].b - pr[i].c; // 计算差值，降序排列，前n个数就是b>c的，后n个用n即可}sort(pr + 1, pr + 2 * n + 1, cmp);ll ans = 0;for(int i = 1; i <= n; i++){ans += pr[i].b;}for(int i = n + 1; i <= 2*n; i++){ans += pr[i].c;}cout << ans;return 0;
}

梦境巡查

#include<bits/stdc++.h>
using namespace std;
int n;
int a[100010], w[100010], b[100010];
void get_min(int lost){int begin = 0;int cur = 0;for(int i = 0; i <= n; i++){if(cur < a[i]){ // 当前值小于a[i]begin += a[i] - cur; // 初始值加上a[i] - curcur = a[i];}cur -= a[i];if(i != lost - 1) cur += b[i + 1];}w[lost] = begin;
}
int main(){ios::sync_with_stdio(0);cin.tie(0);cin >> n;for(int i = 0; i <= n; i++){cin >> a[i];}for(int i = 1; i <= n; i++){cin >> b[i];}for(int i = 1; i <= n; i++){get_min(i);cout << w[i] << " ";}return 0;
}

双指针，高精度，离散化

消消乐

#include<bits/stdc++.h>
using namespace std;
int main(){ios::sync_with_stdio(0);cin.tie(0);string str;cin >> str;int l = 0;int r = str.size() - 1;int ans = str.size();while(l < r){if(str[l] == 'A' && str[r] == 'B'){ans -= 2;l++;r--;}else if(str[l] == 'B') l++;else if(str[r] == 'A') r--;}cout << ans;return 0;
}

A+B(高精度)

#include<bits/stdc++.h>
using namespace std;
vector<int> add(vector<int> &a, vector<int> &b){vector<int> c;int t = 0;for(int i = 0; i < a.size() || i < b.size(); i++){if(i < a.size()) t += a[i];if(i < b.size()) t += b[i];c.push_back(t%10);t /= 10;}if(t) c.push_back(1);return c;
}
int main(){ios::sync_with_stdio(0);cin.tie(0);vector<int> a, b;string sa, sb;cin >> sa >> sb;for(int i = sa.size() - 1; i >= 0; i--) a.push_back(sa[i] - '0');for(int i = sb.size() - 1; i >= 0; i--) b.push_back(sb[i] - '0');vector<int> c = add(a, b);for(int i = c.size() - 1; i >= 0; i--) cout << c[i];return 0;
}

区间和

#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> PII;
const int N = 300010;
int n, m;
int a[N], s[N];
vector<int> alls;
vector<PII> add, query;
int find(int x){int l = 0, r = alls.size() - 1;while(l < r){int mid = l + r >> 1;if(alls[mid] >= x) r = mid;else l = mid + 1;}return r + 1;
}
int main(){ios::sync_with_stdio(0);cin.tie(0);cin >> n >> m;for(int i = 0; i < n; i++){int x, c;cin >> x >> c;add.push_back({x, c});alls.push_back(x);}for(int i = 0; i < m; i++){int l, r;cin >> l >> r;query.push_back({l, r});alls.push_back(l);alls.push_back(r);}sort(alls.begin(), alls.end());alls.erase(unique(alls.begin(), alls.end()), alls.end());for(auto item : add){int x = find(item.first);a[x] += item.second;}for(int i = 1; i <= alls.size(); i++) s[i] = s[i - 1] + a[i];for(auto item : query){int l = find(item.first), r = find(item.second);cout << s[r] - s[l - 1] <<endl;}return 0;
}