Project Euler task 92

A number chain is created by continuously adding the square of the digits in a number to form a new number until it has been seen before.

For example,

44 32 13 10 1 1
85 89 145 42 20 4 16 37 58 89

Therefore any chain that arrives at 1 or 89 will become stuck in an endless loop. What is most amazing is that EVERY starting number will eventually arrive at 1 or 89.

How many starting numbers below ten million will arrive at 89?

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#include < iostream >

using namespace std;

const unsigned int nMaxNum = 10000000;

unsigned int pArray[nMaxNum];

unsigned int getSqrSum(unsigned int _n) {

unsigned int nRes = 0;

while (_n) {

unsigned int nTemp = (_n % 10);

nRes += nTemp * nTemp;

_n /= 10;

}

return nRes;

}

int main() {

memset(pArray, 0, nMaxNum);

unsigned int nSum = 0;

for (int i = 1; i < nMaxNum; i++) {

unsigned int nTemp = i;

while (nTemp != 1 && nTemp != 89) {

nTemp = getSqrSum(nTemp);

if (pArray[nTemp])

nTemp = pArray[nTemp];

}

nSum += (nTemp == 89) ? 1 : 0;

pArray[i] = nTemp;

}

cout << nSum << endl;

return 0;

}