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hdu 5055 Bob and math problem (很简单贪心)

给N个数字(0-9),让你组成一个数。

要求:1.这个数是奇数    2.这个数没有前导0

问这个数最大是多少。

 

思路&解法:

N个数字从大到小排序,将最小的奇数与最后一位交换,把剩下前N-1位从大到小排序。输出。(判断第一位是否为0)

 

代码:

#include <cstdio>#include <iostream>#include <string.h>#include <cstdlib>#include <algorithm>#include <queue>#include <vector>#include <cmath>#include <map>#include <stack>using namespace std;int const uu[4] = {1,-1,0,0};int const vv[4] = {0,0,1,-1};typedef long long ll;int const maxn = 50005;int const inf = 0x3f3f3f3f;ll const INF = 0x7fffffffffffffffll;double eps = 1e-10;double pi = acos(-1.0);#define rep(i,s,n) for(int i=(s);i<=(n);++i)#define rep2(i,s,n) for(int i=(s);i>=(n);--i)#define mem(v,n) memset(v,(n),sizeof(v))#define lson l, m, rt<<1#define rson m+1, r, rt<<1|1int n;int a[105];bool cmp(int a,int b){    return a>b;}int main(){    while(scanf("%d",&n)!=EOF){        rep(i,0,n-1) scanf("%d",&a[i]);        sort(a,a+n,cmp);        int t1=-1;        rep2(i,n-1,0) if(a[i]%2==1){            t1=i;            break;        }        if(t1==-1){            printf("-1\n");            continue;        }        swap(a[t1],a[n-1]);        sort(a,a+n-1,cmp);        if(a[0]==0){            printf("-1\n");            continue;        }        rep(i,0,n-1) printf("%d",a[i]); cout<<endl;    }}

 

hdu 5055 Bob and math problem (很简单贪心)