学步园

/*
*  使用深度优先选择(DFS)算法，给定5个数，写下其中任意3个数的组合
*  使用递归方法，分为1个数、2个数、3个数 三层，并传进起始下标
*/

#include <stdio.h>

#define NUM_ALL 5
#define NUM_SELECT 3

int sum = 0;
int a[6] = {0,1,2,3,4,5};
int index[4];

void SumIsNine()
{
if (sum == 9) {
        printf("Sum is 9: %d,%d,%d\n", index[1], index[2], index[3]);
    } else {
        printf("%d,%d,%d\n", index[1], index[2], index[3]);
    }
}

void Combine(int numA, int indexPre)
{
int indexLast = NUM_ALL - NUM_SELECT + numA;
int indexNow;
for (indexNow = indexPre; indexNow <= indexLast; indexNow++) {
        sum += a[indexNow];
        index[numA] = indexNow;
if (numA == 3) {
            SumIsNine();
        } else {
            Combine(numA+1, indexNow+1);
        }
        sum -= a[indexNow];
    }
}

int main(void)
{
int numA = 1, indexStart = 1;
    Combine(numA, indexStart);
}