题意：求一个数列中所有的绝对值差大于2的数，并用后面的数字减前面的数字的加和。
分析：可以用树状数组每次找前面的差值大于2的数，也可以直接每次加前面所有的数字，再减去差值为1的数字。题目最坑爹的是答案也许会爆long long，可以用long double或者使用unsigned long long手动模拟符号位，或者用python
C++代码：
1 #define _CRT_SECURE_NO_DEPRECATE
2 #pragma comment(linker, "/STACK:102400000,102400000")
3 #include<iostream>
4 #include<cstdio>
5 #include<fstream>
6 #include<iomanip>
7 #include<algorithm>
8 #include<cmath>
9 #include<deque>
10 #include<vector>
11 #include<bitset>
12 #include<queue>
13 #include<string>
14 #include<cstring>
15 #include<map>
16 #include<stack>
17 #include<set>
18 #include<functional>
19 #define pii pair<int, ll>
20 #define mod 1000000007
21 #define mp make_pair
22 #define pi acos(-1)
23 #define eps 0.00000001
24 #define mst(a,i) memset(a,i,sizeof(a))
25 #define all(n) n.begin(),n.end()
26 #define lson(x) ((x<<1))
27 #define rson(x) ((x<<1)|1)
28 #define inf 0x3f3f3f3f
29 typedef long long ll;
30 typedef unsigned long long ull;
31 using namespace std;
32 const int maxn = 2e5 + 50;
33 map<ll, ll>a;
34 int main()
35 {
36 ios::sync_with_stdio(false);
37 cin.tie(0); cout.tie(0);
38 ll i, j, k, m, n;
39 cin >> n;
40 long double ans = 0;
41 ll sum = 0;
42 for (int i = 1; i <= n; ++i)
43 {
44 cin >> m;
45 sum += m;
46 ans += i*m - sum;
47 ans -= a[m - 1];
48 ans += a[m + 1];
49 a[m]++;
50 }
51 cout << setiosflags(ios::fixed) << setprecision(0) << ans << endl;
52 return 0;
53 }
python：
1 n=input() 2 mp = list(map(int,input().split())) 3 sum = 0 4 ans = 0 5 cnt = 0 6 tt = dict() 7 for i in mp: 8 sum+=i 9 cnt=cnt+1 10 ans+=cnt*i-sum 11 if i-1 in tt: 12 ans-=tt[i-1] 13 if i+1 in tt: 14 ans+=tt[i+1] 15 if i not in tt: 16 tt[i]=0 17 tt[i]=tt[i]+1 18 print(ans)
树状数组错误代码（答案爆long long）
1 #define _CRT_SECURE_NO_DEPRECATE
2 #pragma comment(linker, "/STACK:102400000,102400000")
3 #include<iostream>
4 #include<cstdio>
5 #include<fstream>
6 #include<iomanip>
7 #include<algorithm>
8 #include<cmath>
9 #include<deque>
10 #include<vector>
11 #include<bitset>
12 #include<queue>
13 #include<string>
14 #include<cstring>
15 #include<map>
16 #include<stack>
17 #include<set>
18 #include<functional>
19 #define pii pair<int, ll>
20 #define mod 1000000007
21 #define mp make_pair
22 #define pi acos(-1)
23 #define eps 0.00000001
24 #define mst(a,i) memset(a,i,sizeof(a))
25 #define all(n) n.begin(),n.end()
26 #define lson(x) ((x<<1))
27 #define rson(x) ((x<<1)|1)
28 #define inf 0x3f3f3f3f
29 typedef long long ll;
30 typedef unsigned long long ull;
31 using namespace std;
32 const int maxn = 2e5 + 50;
33 ll ori[maxn];
34 int n;
35 ll t[maxn];
36
37 int Lowbit(int x)
38 {
39 return x&(-x);
40 }
41 void update(ll i, ll x)
42 {
43 while (i <= n)
44 {
45 t[i] += x;
46 i += Lowbit(i);
47 }
48 }
49 ll sum(int x)
50 {
51 ll sum = 0;
52 while (x>0)
53 {
54 sum += t[x];
55 x -= Lowbit(x);
56 }
57 return sum;
58 }
59
60 map<ll, ll>id;
61 ll orin[maxn];
62 set<ll>kp;
63 int main()
64 {
65 ios::sync_with_stdio(false);
66 cin.tie(0); cout.tie(0);
67 int i, j, k, m;
68 cin >> n;
69 int cnt = 1;
70 for (int i = 1; i <= n; ++i)
71 {
72 cin >> ori[i];
73 kp.insert(ori[i]);
74 }
75 for (auto it : kp)
76 {
77 orin[cnt] = it;
78 id[it] = cnt++;
79 }
80 for (int i = 1; i <= n; ++i)
81 {
82 int iid = id[ori[i]];
83 update(id[ori[i]], 1);
84 }
85 ll fans = 0;
86 for (int i = 1; i <= n; ++i)
87 {
88 auto it = id.lower_bound(ori[i] + 2);
89 if (it != id.end())
90 {
91 auto ta = sum(n);
92 auto tb = sum(it->second - 1);
93 ll cnt = ta - tb;
94 fans -= cnt*ori[i];
95 }
96 it = id.lower_bound(ori[i] - 1);
97 if (it != id.begin())
98 {
99 it--;
100 ll ta = sum(it->second);
101 fans -= ta*ori[i];
102 }
103 update(id[ori[i]], -1);
104 }
105 mst(t, 0);
106 for (int i = 1; i <= n; ++i)
107 {
108 int iid = id[ori[i]];
109 update(id[ori[i]], 1);
110 }
111
112 for (int i = n; i>= 1; --i)
113 {
114 auto it = id.lower_bound(ori[i] + 2);
115 if (it != id.end())
116 {
117 auto ta = sum(n);
118 auto tb = sum(it->second - 1);
119 ll cnt = ta - tb;
120 fans += cnt*ori[i];
121 }
122 it = id.lower_bound(ori[i] - 1);
123 if (it != id.begin())
124 {
125 it--;
126 ll ta = sum(it->second);
127 fans += ta*ori[i];
128 }
129 update(id[ori[i]], -1);
130 }
131 cout << fans << endl;
132 return 0;
133 }
原文地址：https://www.cnblogs.com/Meternal/p/8119807.html
时间： 2024-11-02 17:22:58