递归专题
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int n, r, x[25], len;
void work() {
if (len == r) {
for (int i=0; i<r; i++) printf("%3d", x[i]);
printf("\n");
return;
}
int last = len>0 ? x[len-1]+1 : 1;
for (int i=last; i<=n; i++) { // 保证后面选择的数比前面都大
x[len++] = i;
work();
len--; // 回溯
}
}
int main() {
scanf("%d %d", &n, &r);
work();
return 0;
}
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int M, N, x[15], len, sum, K;
void work() {
if (len == N) {
if (sum == M) K++;
return;
}
int last = len>0 ? x[len-1] : 0;
for (int i=last; i<= M-sum; i++) {
x[len++] = i;
sum += i;
work();
sum -= i;
len--;
}
}
int main() {
int T; scanf("%d", &T);
while (T--) {
K = 0;
scanf("%d %d", &M, &N);
work();
printf("%d\n", K);
}
return 0;
}
