取150个随机数,总和等于20000

不太均匀
import java.util.*;
public class T1013 {
public static void main(String args[]){
Random rnd = new Random();
int sum = 20000;
int tmp = sum;
for(int i=0; i<149; i++){
int next = rnd.nextInt(tmp);
System.out.println(next);
tmp -= next;
}
System.out.println(tmp);
}
}

不用那么麻烦，一个循环就可以了int max = 20000;
int[] num = new int[150];
for (int i=0; i<149; i++) {
    num[i] = (int)(Math.random()*max); //生成随技术
    System.out.print("num["+i+"]="+num[i]+",");
    max -= num[i]; //不断地减去生成的随机数
}
num[149] = max;
System.out.print("num[149]="+max);

qybao(阿宝)的方法很好
不过我觉得产生随机数时乘的那个数要根据要求的范围来确定
如果用MAX的话后面肯定有一大堆随机数都是零。

同意fengxin09(星缘)
随即数的生成应该规定服从某个分布
比如说均值为（20000/150）的正态分布

believefym(暮色，miss，迷失，miss)用的是JDK里的java.util.Random类qybao(阿宝)用的是java.lang.Math.random()静态方法，由于是一个静态方法，所以使用时可以不通过Math对象，调用此方法，会先创建出一个Random对象两个人的for循环本质是一样的不过我试了n次，只有前面10来个是正常的数字，以后的都是0了，非常有意思的是最后一个都是1

qybao(阿宝)的方法很好
不过我觉得产生随机数时乘的那个数要根据要求的范围来确定
如果用MAX的话后面肯定有一大堆随机数都是零。
----------------------------------------------
避免出现一大堆0的情况，稍微改改就可以了
int max = 20000;
int[] num = new int[150];
int count = 150; //平均数
for (int i=0; i<149; i++) {
    num[i] = (int)(Math.random()*max/count--); //max/count，取平均数的随机数
    System.out.print("num["+i+"]="+num[i]+",");
    max -= num[i]; //不断地减去生成的随机数
}
num[149] = max;
System.out.print("num[149]="+max);

qybao(阿宝) 真乃神人也.不过,还是没解决问题. 会有负数出现.

to Riddick2046(神为) ( )
会有负数出现？请问是哪一步？或者你运行过了？
我只是按逻辑分析
首先0<=Math.random()<=1，所以 0<=(Math.random()*max/count--)<=max
即 num[i]总是小于或等于max
所以max=max-num[i]总是大于等于0
两个大于等于0的数相乘又怎么会出现负数呢？

int max = 20000/150*2; //根据正态分布和随机数原理,应该设置平均值的2倍作为极限值比较合理
int[] num = new int[150];
int sum =0;
for (int i=0; i<150/2; i++) {
    num[i] = (int)(Math.random()*max); //生成一个随机数
    num[149-i] = max - num[i]; //每次生成一对随机数,每对随机数的和为max,这样保证了所有随机数总和为20000
    System.out.print("num["+i+"]="+num[i]+",");
    System.out.print("num["+(149-i)+"]="+num[149-i]+",");
    sum+=num[i];
    sum+=num[149-i];
}
System.out.print("sum="+sum);

楼上的，sum=19950，这个是怎么回事

to qybao(阿宝)
为啥我运行你那代码后，SUM总不是等于2W呢？

to qingyun1136(执迷不悟):int max = 20000/150*2; 这句话就有问题吧，这样得出的MAX会直接导致最后的结果不正确

package jimi;public class test {
public static void main(String[] agrs){
int max = 20000;
int num = 150;
int [] result = new int[num];

while(max>0){
int temp = getAmount(1);
if(max<=temp){
result[getRandomPos(num)]+=max;

}else{
result[getRandomPos(num)]+=temp;
}
max-=temp;
}
int sum = 0;
for(int i=0;i<150;i++){
System.out.println("result["+i+"] = "+result[i]);
sum += result[i];
}
System.out.println("sum = "+sum);
}
public static int  getRandomPos(int num){
return (int)(getRandom()*num);
}
public static int  getAmount(int precision){
return (int)(getRandom()*precision +1);
}
public  static double  getRandom(){
return ((int)(Math.random()*1000))/1000.0;
}
}

其中getAmount(int precision)中的参数为分配的精度，越小越均匀，越大越差别大，具体的随机数的分布方式我不知道，需要进一步的数学验证

感谢 zoeg(沉香) 的那一段话

to qybao(阿宝)
为啥我运行你那代码后，SUM总不是等于2W呢？
-----------------------------------------
不知你是怎么相加不等于2W的？
你再验证试试
int max = 20000;
int[] num = new int[150];
int count = 150; //平均数
for (int i=0; i<149; i++) {
    num[i] = (int)(Math.random()*max/count--); //max/count，取平均数的随机数
    System.out.print("num["+i+"]="+num[i]+",");
    max -= num[i]; //不断地减去生成的随机数
}
num[149] = max;
System.out.print("num[149]="+max);
//验证
int sum = 0;
for (int i=0; i<150; i++) {
    sum += num[i];
}
System.out.print("sum="+sum);

precision参数为1时的一次运行结果
result[0] = 151
result[1] = 122
result[2] = 115
result[3] = 128
result[4] = 117
result[5] = 117
result[6] = 137
result[7] = 137
result[8] = 127
result[9] = 144
result[10] = 170
result[11] = 125
result[12] = 154
result[13] = 141
result[14] = 132
result[15] = 145
result[16] = 154
result[17] = 124
result[18] = 138
result[19] = 136
result[20] = 109
result[21] = 144
result[22] = 121
result[23] = 129
result[24] = 128
result[25] = 120
result[26] = 115
result[27] = 148
result[28] = 137
result[29] = 110
result[30] = 134
result[31] = 143
result[32] = 121
result[33] = 144
result[34] = 164
result[35] = 152
result[36] = 141
result[37] = 131
result[38] = 126
result[39] = 143
result[40] = 167
result[41] = 109
result[42] = 128
result[43] = 147
result[44] = 126
result[45] = 121
result[46] = 140
result[47] = 111
result[48] = 142
result[49] = 141
result[50] = 105
result[51] = 150
result[52] = 141
result[53] = 98
result[54] = 157
result[55] = 142
result[56] = 120
result[57] = 158
result[58] = 131
result[59] = 114
result[60] = 149
result[61] = 145
result[62] = 117
result[63] = 129
result[64] = 112
result[65] = 129
result[66] = 155
result[67] = 145
result[68] = 121
result[69] = 152
result[70] = 143
result[71] = 134
result[72] = 134
result[73] = 116
result[74] = 118
result[75] = 138
result[76] = 149
result[77] = 136
result[78] = 127
result[79] = 139
result[80] = 127
result[81] = 147
result[82] = 126
result[83] = 114
result[84] = 128
result[85] = 134
result[86] = 124
result[87] = 123
result[88] = 146
result[89] = 130
result[90] = 146
result[91] = 138
result[92] = 135
result[93] = 134
result[94] = 136
result[95] = 107
result[96] = 141
result[97] = 139
result[98] = 112
result[99] = 143
result[100] = 121
result[101] = 131
result[102] = 124
result[103] = 127
result[104] = 121
result[105] = 140
result[106] = 143
result[107] = 118
result[108] = 137
result[109] = 140
result[110] = 123
result[111] = 143
result[112] = 135
result[113] = 125
result[114] = 151
result[115] = 151
result[116] = 119
result[117] = 127
result[118] = 133
result[119] = 111
result[120] = 139
result[121] = 156
result[122] = 140
result[123] = 126
result[124] = 116
result[125] = 101
result[126] = 119
result[127] = 140
result[128] = 117
result[129] = 142
result[130] = 146
result[131] = 128
result[132] = 145
result[133] = 148
result[134] = 107
result[135] = 148
result[136] = 144
result[137] = 124
result[138] = 146
result[139] = 143
result[140] = 115
result[141] = 162
result[142] = 164
result[143] = 104
result[144] = 153
result[145] = 145
result[146] = 114
result[147] = 137
result[148] = 130
result[149] = 141
sum = 20000

precision参数为50时的一次运行结果
result[0] = 108
result[1] = 121
result[2] = 111
result[3] = 245
result[4] = 140
result[5] = 70
result[6] = 169
result[7] = 207
result[8] = 83
result[9] = 158
result[10] = 72
result[11] = 131
result[12] = 106
result[13] = 90
result[14] = 167
result[15] = 134
result[16] = 154
result[17] = 132
result[18] = 220
result[19] = 155
result[20] = 23
result[21] = 131
result[22] = 168
result[23] = 88
result[24] = 89
result[25] = 70
result[26] = 74
result[27] = 274
result[28] = 278
result[29] = 182
result[30] = 265
result[31] = 279
result[32] = 35
result[33] = 138
result[34] = 112
result[35] = 170
result[36] = 213
result[37] = 57
result[38] = 129
result[39] = 146
result[40] = 121
result[41] = 86
result[42] = 154
result[43] = 86
result[44] = 69
result[45] = 161
result[46] = 213
result[47] = 80
result[48] = 106
result[49] = 169
result[50] = 84
result[51] = 36
result[52] = 103
result[53] = 126
result[54] = 20
result[55] = 114
result[56] = 165
result[57] = 327
result[58] = 119
result[59] = 161
result[60] = 95
result[61] = 170
result[62] = 95
result[63] = 313
result[64] = 68
result[65] = 172
result[66] = 213
result[67] = 93
result[68] = 130
result[69] = 180
result[70] = 68
result[71] = 55
result[72] = 197
result[73] = 135
result[74] = 156
result[75] = 174
result[76] = 29
result[77] = 84
result[78] = 93
result[79] = 100
result[80] = 77
result[81] = 110
result[82] = 146
result[83] = 113
result[84] = 202
result[85] = 237
result[86] = 95
result[87] = 101
result[88] = 121
result[89] = 166
result[90] = 121
result[91] = 125
result[92] = 68
result[93] = 122
result[94] = 72
result[95] = 143
result[96] = 22
result[97] = 139
result[98] = 74
result[99] = 173
result[100] = 166
result[101] = 51
result[102] = 231
result[103] = 144
result[104] = 96
result[105] = 184
result[106] = 135
result[107] = 129
result[108] = 137
result[109] = 73
result[110] = 183
result[111] = 168
result[112] = 202
result[113] = 129
result[114] = 155
result[115] = 167
result[116] = 43
result[117] = 9
result[118] = 91
result[119] = 129
result[120] = 77
result[121] = 275
result[122] = 125
result[123] = 162
result[124] = 85
result[125] = 113
result[126] = 91
result[127] = 174
result[128] = 150
result[129] = 83
result[130] = 103
result[131] = 92
result[132] = 172
result[133] = 188
result[134] = 64
result[135] = 218
result[136] = 279
result[137] = 40
result[138] = 61
result[139] = 112
result[140] = 168
result[141] = 186
result[142] = 179
result[143] = 47
result[144] = 75
result[145] = 242
result[146] = 210
result[147] = 96
result[148] = 208
result[149] = 62
sum = 20000

支持cly33(jim)，不过楼主的150个随机数好像不一定是int型哦

调试易

取150个随机数,总和等于20000

解决方案 »