题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5504
思路：模拟
代码：
1 #include<stdio.h>//------杭电5504 2 #include<algorithm> 3 #include<math.h> 4 #include<iostream> 5 using namespace std; 6 int comp(const void*a, const void*b) 7 { 8 return *(int*)a - *(int*)b; 9 } 10 int main() 11 { 12 int t; 13 scanf("%d", &t); 14 while (t) 15 { 16 __int64 *a; 17 int n; 18 int count1 = 0;//记录负数 19 int count2 = 0;//记录0 20 int count3 = 0;//记录正数 21 int i; 22 __int64 result = 1; 23 __int64 maxx = -0x3f3f3f3f; 24 scanf("%d", &n); 25 a = (__int64*)malloc(n*sizeof(__int64)); 26 for (i = 0; i < n; i++) 27 { 28 scanf("%I64d", (a + i)); 29 if (a[i] < 0) 30 { 31 count1++; 32 maxx = max(maxx, a[i]); 33 } 34 else if (a[i]>0) 35 count3++; 36 else 37 count2++; 38 } 39 qsort(a, n, sizeof(__int64), comp);//对数组排序 40 if (count1 == 0)//没有负数 41 { 42 if (count3 != 0) 43 { 44 if (count2 == 0) 45 i = 0; 46 else 47 i = count2; 48 for (i; i < n; i++) 49 { 50 result *= a[i]; 51 } 52 } 53 else if (count3 == 0)//无正数 54 { 55 result = 0; 56 } 57 } 58 else if (count1 == 1)//只有一个负数 59 { 60 if (count3 != 0) 61 { 62 if (count2 == 0) 63 i = 1; 64 else 65 i = count2 + count1; 66 for (i; i < n; i++) 67 { 68 result *= a[i]; 69 } 70 } 71 else if (count3 == 0)//无正数 72 { 73 if (count2 == 0) 74 result *= a[0]; 75 else 76 result = 0; 77 } 78 } 79 else if (count1 % 2 == 0)//偶数个负数 80 { 81 for (i = 0; i < count1; i++) 82 { 83 result *= a[i]; 84 } 85 if (count3 != 0) 86 { 87 if (count2 == 0) 88 i = count1; 89 else 90 i = count2 + count1; 91 for (i; i < n; i++) 92 { 93 result *= a[i]; 94 } 95 } 96 else if (count3 == 0)//无正数，值保留 97 { 98 result = result; 99 } 100 } 101 else if (count1 % 2 != 0)//奇数个负数 102 { 103 for (i = 0; i < count1-1; i++) 104 { 105 result *= a[i]; 106 } 107 if (count3 != 0) 108 { 109 if (count2 == 0) 110 i = count1; 111 else 112 i = count2 + count1; 113 for (i; i < n; i++) 114 { 115 result *= a[i]; 116 } 117 } 118 else if (count3 == 0)//无正数，值保留 119 { 120 result = result; 121 } 122 } 123 printf("%I64d ", result); 124 t--; 125 } 126 return 0; 127 }