NYOJ-组合数

NYOJ-组合数

#include<cstdio>
#include<algorithm>
#include<iostream>
using namespace std;
int n, r;
bool isD(string s) {
char c1 = s[0];
for (int i = 1; i < r; i++) {
if (c1 < s[i]) return false;
c1 = s[i];
}
return true;
}
int main() {
//freopen("in.txt", "r", stdin);
string s1;
scanf("%d%d", &n, &r);
for (int i = n; i > 0; i--) {
s1 += '0' + i;
}
string s2;
while(prev_permutation(s1.begin(), s1.end())) {
if (isD(s1) && s2 != s1.substr(0, r)){
s2 = s1.substr(0, r);
cout << s2 << endl;
}
}

return 0;
}

#include<cstdio>
#include<cstdlib>
int box[11], book[11], n;
void dfs(int step, int count) {

if (count >= n+1) {
for (int i = 0; i < n; i++) {
printf("%d",box[i]);
}
puts("");
if (box[0] == n) exit(-1);
return;
}

// 尝试处理每一种可能
for (int i = step; i > 0; i--) {
box[count-1] = step--;
dfs(step, count+1);
}

}

int main() {
//  freopen("in.txt","r",stdin);     //从in.txt 中读入数据
int m;
scanf("%d%d", &m, &n);
dfs(m, 1);
return 0;
}