# （*）剑指offer 面试题43：n个骰子的点数

n个骰子的点数之和最小为n，最大值为6n，n个骰子的所有点数的排列数为6^n，需要先统计出每一个点数出现的次数。

``````int g_maxValue = 6;
void printProbability(int number) {
if (number < 1)  return;
int maxSum = number*g_maxValue;
int  *pProbability = new int[maxSum - number + 1];
for (int i = number; i <= maxSum; ++i) {
pProbability[i - number] = 0;
}
probability(number, pProbability);
int total = pow(g_maxValue, number);
for (int i = number; i <= maxSum; ++i) {
double ratio = (double)pProbablity[i-number]/total;
cout << ratio;
}
delete[] pProbability;
}

void probability(int number, int* pProbability) {
for (int i = 1; i <= g_maxValue; ++i) {
probabilityCore(number, number, i, 0, pProbability);
}
}

void probabilityCore(int original, int current, int value, int tmpSum, int* pProbability) {
if (current == 1) {
int sum = value + tmpSum;
++pProbability[sum - original];
} else {
for (int i = 1; i <= g_maxValue; ++i) {
int sum = value + tmpSum;
probabilityCore(original, current-1, i, sum, pProbability);
}
}
}
``````

``````void printProbability(int number) {
if (number < 1)  return;
int* pProbabilities[2];
pProbabilities[0] = new int[g_maxValue * number + 1];
pProbabilities[1] = new int[g_maxValue * number + 1];
for (int i = 0; i < g_maxValue * number + 1; ++i) {
pProbabilities[0][i] = 0;
pProbabilities[1][i] = 0;
}

int flag = 0;
for (int i = 1; i <= g_maxValue; ++i) {
pProbabilities[flag][i] = 1;
}
for (int k = 2; k <= number; ++k) {
for (int i = 0; i < k; ++i) {
pProbabilities[1-flag][i] = 0;
}
for (int i = 1*k; i <= g_maxValue*k; ++i) {
pProbabilities[1-flag][i] = 0;
for (int j = 1; j <= i && j <= g_maxValue; ++j) {
pProbabilities[1-flag][i] += pProbabilities[flag][i-j];
}
}
flag = 1 - flag;
}
double total = pow((double)g_maxValue, number);
for (int i = number; i <= g_maxValue * number; ++i) {
double ratio = (double)pProbabilities[flag][i]/total;
cout << ratio;
}
delete[] pProbabilities[0];
delete[] pProbabilities[1];
}
``````