HDU ACM 1496 Equations
Equations
Time Limit: 6000/3000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3978 Accepted Submission(s): 1602
Problem Description
Consider equations having the following form:
a*x1^2+b*x2^2+c*x3^2+d*x4^2=0
a, b, c, d are integers from the interval [-50,50] and any of them cannot be 0.
It is consider a solution a system ( x1,x2,x3,x4 ) that verifies the equation, xi is an integer from [-100,100] and xi != 0, any i ∈{1,2,3,4}.
Determine how many solutions satisfy the given equation.
a*x1^2+b*x2^2+c*x3^2+d*x4^2=0
a, b, c, d are integers from the interval [-50,50] and any of them cannot be 0.
It is consider a solution a system ( x1,x2,x3,x4 ) that verifies the equation, xi is an integer from [-100,100] and xi != 0, any i ∈{1,2,3,4}.
Determine how many solutions satisfy the given equation.
Input
The input consists of several test cases. Each test case consists of a single line containing the 4 coefficients a, b, c, d, separated by one or more blanks.
End of file.
End of file.
Output
For each test case, output a single line containing the number of the solutions.
Sample Input
1 2 3 -4
1 1 1 1
Sample Output
39088
0
Author
LL
Recommend
LL
解题思路:暴力+hash,主要是想练练hash,一直认为hash是高端黑,用线性探测再散列处理冲突,记得不知道谁说过处理余数的数一般用上素数,不要忘了最后乘上16,因为四个数有可能是正负
1 #include<stdio.h> 2 #include<string.h> 3 #define MAXN 50001 4 int num[MAXN], store[MAXN]; 5 6 int hash(int cur) 7 { 8 int temp = cur%MAXN; 9 if(temp < 0) temp += MAXN; 10 while(num[temp] != 0 && store[temp] != cur) 11 { 12 temp = (temp+1)%MAXN; 13 } 14 return temp; 15 } 16 17 int main() 18 { 19 // freopen("input.txt", "r", stdin); 20 int rate[101], a, b, c, d, i, j, sum, temp, res; 21 for(i=0; i<101; ++i) rate[i] = i*i; 22 while(scanf("%d%d%d%d", &a, &b, &c, &d) != EOF) 23 { 24 if((a>0&&b>0&&c>0&&d>0) || (a<0&&b<0&&c<0&&d<0)) 25 { 26 printf("0\n"); 27 continue; 28 } 29 memset(num, 0, sizeof(num)); 30 for(i=1; i<101; ++i) 31 for(j=1; j<101; ++j) 32 { 33 temp = a*rate[i]+b*rate[j]; 34 res = hash(temp); 35 store[res] = temp; 36 num[res]++; 37 } 38 39 sum = 0; 40 41 for(i=1; i<101; ++i) 42 for(j=1; j<101; ++j) 43 { 44 temp = -(c*rate[i]+d*rate[j]); 45 res = hash(temp); 46 sum += num[res]; 47 } 48 49 printf("%d\n", sum*2*2*2*2); 50 } 51 return 0; 52 }
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作者:雪影蓝枫
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