Mr. Frog’s Problem
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 312 Accepted Submission(s): 219Problem DescriptionOne day, you, a clever boy, feel bored in your math class, and then fall asleep without your control. In your dream, you meet Mr. Frog, an elder man. He has a problem for you.
He gives you two positive integers A and B, and your task is to find all pairs of integers (C, D), such that A≤C≤B,A≤D≤B and AB+BA≤CD+DC
Inputfirst line contains only one integer T (T≤125), which indicates the number of test cases. Each test case contains two integers A and B (1≤A≤B≤1018).
OutputFor each test case, first output one line "Case #x:", where x is the case number (starting from 1).
Then in a new line, print an integer s indicating the number of pairs you find.
In each of the following s lines, print a pair of integers C and D. pairs should be sorted by C, and then by D in ascending order.
Sample Input2 10 10 9 27
Sample OutputCase #1: 1 10 10 Case #2: 2 9 27 27 9
Source
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题目链接：
http://acm.hdu.edu.cn/showproblem.php?pid=5924
题目大意：
题目给定A和B(<=1018)，求满足
的C和D个个数，并全部输出。
题目思路：
【模拟】
+1s 这题一看样例就猜大概只有AB，BA两种情况。不妨假设C<=D
假设A/B+B/A>A/(B-1)+(B-1)/A，解得条件为B2-B>A2,所以如果要满足，则需要A2>=B2-B，而只有当A=B时满足(B>=A,B=A+1时，B2-B=A(A+1)>A2)
所以除了A=B的情况，其余都是减的，(C,D)可视为(A,B)->(A,D)->(C,D)，每次只改一维，递减，所以最终也是递减的。
所以最终答案就是AB,BA 注意A=B的情况。
1 //HDU 5924 2 //by coolxxx 3 //#include<bits/stdc++.h> 4 #include<iostream> 5 #include<algorithm> 6 #include<string> 7 #include<iomanip> 8 #include<map> 9 #include<stack> 10 #include<queue> 11 #include<set> 12 #include<bitset> 13 #include<memory.h> 14 #include<time.h> 15 #include<stdio.h> 16 #include<stdlib.h> 17 #include<string.h> 18 //#include<stdbool.h> 19 #include<math.h> 20 #pragma comment(linker,"/STACK:1024000000,1024000000") 21 #define min(a,b) ((a)<(b)?(a):(b)) 22 #define max(a,b) ((a)>(b)?(a):(b)) 23 #define abs(a) ((a)>0?(a):(-(a))) 24 #define lowbit(a) (a&(-a)) 25 #define sqr(a) ((a)*(a)) 26 #define swap(a,b) ((a)^=(b),(b)^=(a),(a)^=(b)) 27 #define mem(a,b) memset(a,b,sizeof(a)) 28 #define eps (1e-10) 29 #define J 10000 30 #define mod 1000000007 31 #define MAX 0x7f7f7f7f 32 #define PI 3.14159265358979323 33 #define N 100004 34 using namespace std; 35 typedef long long LL; 36 double anss; 37 LL aans; 38 int cas,cass; 39 LL n,m,lll,ans; 40 41 int main() 42 { 43 #ifndef ONLINE_JUDGEW 44 // freopen("1.txt","r",stdin); 45 // freopen("2.txt","w",stdout); 46 #endif 47 int i,j,k; 48 int x,y,z; 49 // init(); 50 // for(scanf("%d",&cass);cass;cass--) 51 for(scanf("%d",&cas),cass=1;cass<=cas;cass++) 52 // while(~scanf("%s",s)) 53 // while(~scanf("%d%d",&n,&m)) 54 { 55 printf("Case #%d:\n",cass); 56 scanf("%lld%lld",&n,&m); 57 if(n==m)printf("%d\n%lld %lld\n",1,n,m); 58 else printf("%d\n%lld %lld\n%lld %lld\n",2,n,m,m,n); 59 } 60 return 0; 61 } 62 /* 63 // 64 65 // 66 */
HDU 5924 Mr. Frog’s Problem 【模拟】 (2016CCPC东北地区大学生程序设计竞赛)
原文：http://www.cnblogs.com/Coolxxx/p/5982255.html
