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The Diophantine Equation hdu 3270
每天一题萌萌哒
The Diophantine Equation
Time Limit: 1000/500 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 1130 Accepted Submission(s): 290
Problem Description
We will consider a linear Diaphonic equation here and you are to find out whether the equation is solvable in non-negative integers or not.
Easy, is not it?
Easy, is not it?
Input
There will be multiple cases. Each case will consist of a single line expressing the Diophantine equation we want to solve. The equation will be in the form ax + by = c. Here a and b are two positive integers expressing the co-efficient of two variables x and y.
There are spaces between:
1. “ax” and ‘+’
2. ‘+’ and “by”
3. “by” and ‘=’
4. ‘=’ and “c”
c is another integer that express the result of ax + by. -1000000<c<1000000. All other integers are positive and less than 100000. Note that, if a=1 then ‘ax’ will be represented as ‘x’ and same for by.
There are spaces between:
1. “ax” and ‘+’
2. ‘+’ and “by”
3. “by” and ‘=’
4. ‘=’ and “c”
c is another integer that express the result of ax + by. -1000000<c<1000000. All other integers are positive and less than 100000. Note that, if a=1 then ‘ax’ will be represented as ‘x’ and same for by.
Output
You should output a single line containing either the word “Yes.” or “No.” for each input cases resulting either the equation is solvable in non-negative integers or not. An equation is solvable in non-negative integers if for non-negative integer value of x and y the equation is true. There should be a blank line after each test cases. Please have a look at the sample input-output for further clarification.
Sample Input
2x + 3y = 10 15x + 35y = 67 x + y = 0
Sample Output
Yes. No. Yes. HINT: The first equation is true for x = 2, y = 2. So, we get, 2*2 + 3*2=10. Therefore, the output should be “Yes.”
Author
Muhammed Hedayet
Source
HDOJ Monthly Contest – 2010.01.02
题意:就是用扩展的欧几里得定理,如果有不懂得话就访问这个链接吧点击打开链接
既然知道姿势了就非常简单了可以把这个代码记下来,感觉一般求不定方程都一样:
#include <stdio.h> #include <string.h> char str[100]; long long gcd(long long x,long long y) { return y==0?x:gcd(y,x%y); } long long gcd(long x,long y) { return y==0?x:gcd(y,x%y); } long long Ex_Euclid(long long a,long long b,long long &x,long long &y) { long long ans,t; if (b==0) { x=1; y=0; ans=0; return ans; } ans=Ex_Euclid(b,a%b,x,y); t=x; x=y; y=t-(a/b)*y; return ans; } int main() { int i,j,n; long long A,B,C,D,x,y,k,t; while(scanf("%s",str)!=EOF) { A=0; for (i=0;i<strlen(str)-1;i++) { A=A*10+str[i]-'0'; } scanf("%s",str); scanf("%s",str); B=0; for (i=0;i<strlen(str)-1;i++) { B=B*10+str[i]-'0'; } scanf("%s",str); scanf("%s",str); C=0; for (i=0;i<strlen(str);i++) { C=C*10+str[i]-'0'; } if (A==0) A=1; if (B==0) B=1; D=gcd(A,B); if (C%D!=0) { printf("No.\n\n"); continue; } n=Ex_Euclid(A,B,x,y); x=x*C/D; t=B/D; x=(x%t+t)%t; k=(C-A*x)/B; if (k>=0) { printf("Yes.\n\n"); continue; } y=y*C/D; t=A/D; y=(y%t+t)%t; k=(C-B*y)/A; if (k>=0) { printf("Yes.\n\n"); continue; } printf("No.\n\n"); } return 0; }
这个题除了用扩展的欧几里得还可以用直接暴搜,感觉是不是很暴力:
#include<cstdio> #include<cstring> #include<cstdlib> char arr[30],temp[10]; int a,b,c; int main() { int i,j,len,x,y,cnt; while(scanf("%s",temp)!=EOF) { getchar();getchar();getchar(); a=atoi(temp); if(a==0) a=1; scanf("%s",temp); getchar();getchar();getchar(); b=atoi(temp); if(b==0) b=1; scanf("%d",&c); getchar(); if(c>=0) { if(b==0&&c%a==0||a==0&&c%b==0) { printf("Yes.\n\n"); break; } for(x=0;(cnt=c-a*x)>=0;x++) { if(cnt%b==0) { printf("Yes.\n\n"); break; } } if(cnt<0) printf("No.\n\n"); } else printf("No.\n\n"); } return 0; }
稍稍的解释一下公式吧:ax+by=c ;
y=(c-ax)/b;记住分子要大于0,很简单吧。
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