[HDOJ5742]It's All In The Mind（贪心）

Posted 2020-08-04

题目链接：http://acm.split.hdu.edu.cn/showproblem.php?pid=5742

题意：给出一个不递增数列的其中几个数字，还有一些数字不知道，如何填写不知道的那些数字使得这个数的前两位之和与总数之和最小。

先贪心把前两位补上，如果a1没有，那a1就是100，同时如果a2没有则a2=a1。

然后倒着扫描，看到-1直接补0，如果不是-1则更新接下来要填的数。

  1 /*
  2 ━━━━━┒ギリギリ♂ eye！
  3 ┓┏┓┏┓┃キリキリ♂ mind！
  4 ┛┗┛┗┛┃＼○／
  5 ┓┏┓┏┓┃ /
  6 ┛┗┛┗┛┃ノ)
  7 ┓┏┓┏┓┃
  8 ┛┗┛┗┛┃
  9 ┓┏┓┏┓┃
 10 ┛┗┛┗┛┃
 11 ┓┏┓┏┓┃
 12 ┛┗┛┗┛┃
 13 ┓┏┓┏┓┃
 14 ┃┃┃┃┃┃
 15 ┻┻┻┻┻┻
 16 */
 17 #include <algorithm>
 18 #include <iostream>
 19 #include <iomanip>
 20 #include <cstring>
 21 #include <climits>
 22 #include <complex>
 23 #include <fstream>
 24 #include <cassert>
 25 #include <cstdio>
 26 #include <bitset>
 27 #include <vector>
 28 #include <deque>
 29 #include <queue>
 30 #include <stack>
 31 #include <ctime>
 32 #include <set>
 33 #include <map>
 34 #include <cmath>
 35 using namespace std;
 36 #define fr first
 37 #define sc second
 38 #define cl clear
 39 #define BUG puts("here!!!")
 40 #define W(a) while(a--)
 41 #define pb(a) push_back(a)
 42 #define Rint(a) scanf("%d", &a)
 43 #define Rs(a) scanf("%s", a)
 44 #define Cin(a) cin >> a
 45 #define FRead() freopen("in", "r", stdin)
 46 #define FWrite() freopen("out", "w", stdout)
 47 #define Rep(i, len) for(int i = 0; i < (len); i++)
 48 #define For(i, a, len) for(int i = (a); i < (len); i++)
 49 #define Cls(a) memset((a), 0, sizeof(a))
 50 #define Clr(a, x) memset((a), (x), sizeof(a))
 51 #define Full(a) memset((a), 0x7f7f7f, sizeof(a))
 52 #define lrt rt << 1
 53 #define rrt rt << 1 | 1
 54 #define pi 3.14159265359
 55 #define RT return
 56 #define lowbit(x) x & (-x)
 57 #define onecnt(x) __builtin_popcount(x)
 58 typedef long long LL;
 59 typedef long double LD;
 60 typedef unsigned long long ULL;
 61 typedef pair<int, int> pii;
 62 typedef pair<string, int> psi;
 63 typedef pair<LL, LL> pll;
 64 typedef map<string, int> msi;
 65 typedef vector<int> vi;
 66 typedef vector<LL> vl;
 67 typedef vector<vl> vvl;
 68 typedef vector<bool> vb;
 69 
 70 const int maxn = 110;
 71 int n, m;
 72 int a[maxn];
 73 int cur;
 74 
 75 int gcd(int x, int y) {
 76     return y == 0 ? x : gcd(y, x % y);
 77 }
 78 
 79 int main() {
 80     // FRead();
 81     int T;
 82     Rint(T);
 83     int x, y;
 84     W(T) {
 85         Rint(n); Rint(m);
 86         Clr(a, -1);
 87         Rep(i, m) {
 88             Rint(x); Rint(y);
 89             a[x] = y;
 90         }
 91         if(a[1] == -1) {
 92             a[1] = 100;
 93             if(a[2] == -1) a[2] = 100;
 94         }
 95         else {
 96             if(a[2] == -1) a[2] = a[1];
 97         }
 98         int cur = 0;
 99         for(int i = n; i >= 3; i--) {
100             if(a[i] == -1) {
101                 a[i] = cur;
102             }
103             cur = a[i];
104         }
105         int p = a[1] + a[2], q = 0;
106         For(i, 1, n+1) q += a[i];
107         int ex = gcd(p, q);
108         printf("%d/%d\n", p/ex, q/ex);
109     }
110     RT 0;
111 }