CSU-ACM2014年校队选拔赛指导赛解题报告

•Problem A  CSU 1065                               贪心

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 1000010;
struct Node{
    int a,b;
    bool operator < (const Node& rhs) const{
        return b < rhs.b;
    }
}node[maxn];

int main(){
    int n,r = -1,ans = 0;
    scanf("%d",&n);
    for(int i = 0;i < n;i++){
        scanf("%d%d",&node[i].a,&node[i].b);
    }
    sort(node,node+n);
    for(int i = 0;i < n;i++){
        if(node[i].a > r){
            ans++;
            r = node[i].b;
        }
    }
    printf("%d
",ans);
    return 0;
}

•Problem B  CSU 1060                                DP

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 110;
char s1[maxn],s2[maxn],s3[maxn];
int dp[maxn][maxn][maxn];

int main(){
    while(scanf("%s",s1+1) != EOF){
        scanf("%s",s2+1);
        scanf("%s",s3+1);
        int len1 = strlen(s1+1);
        int len2 = strlen(s2+1);
        int len3 = strlen(s3+1);
        memset(dp,0,sizeof(dp));

        for(int i = 1;i <= len1;i++){
            for(int j = 1;j <= len2;j++){
                for(int k = 1;k <= len3;k++){
                    if(s1[i] == s2[j] && s2[j] == s3[k]){
                        dp[i][j][k] = dp[i-1][j-1][k-1]+1;
                    }else{
                        int tmp1 = dp[i-1][j][k];
                        int tmp2 = dp[i][j-1][k];
                        int tmp3 = dp[i][j][k-1];
                        tmp1 = max(tmp1,tmp2);
                        tmp1 = max(tmp1,tmp3);
                        dp[i][j][k] = tmp1;
                    }
                }
            }
        }

        printf("%d
",dp[len1][len2][len3]);
    }
    return 0;
}

•Problem C  CSU 1307                               最短路

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
typedef pair<int,int> pii;
const int maxn = 2010;
const int maxm = 100010;
int v[maxm],next[maxm],w[maxm];
int d[maxm],first[maxn],e;
void init(){
    e = 0;
    memset(first,-1,sizeof(first));
}

void add_edge(int a,int b,int c){
    v[e] = b;next[e] = first[a];w[e] = c;first[a] = e++;
}

int dijkstra(int src,int dist,int mid){
    priority_queue <pii,vector<pii>,greater<pii> > q;
    memset(d,-1,sizeof(d));
    d[src] = 0;
    q.push(make_pair(0,src));
    while(!q.empty()){
        while(!q.empty() && q.top().first > d[q.top().second])  q.pop();
        if(q.empty())   break;
        int u = q.top().second;
        q.pop();
        for(int i = first[u];i != -1;i = next[i])if(w[i] <= mid){
            if(d[v[i]] > d[u] + w[i] || d[v[i]] == -1){
                d[v[i]] = d[u]+w[i];
                q.push(make_pair(d[v[i]],v[i]));
            }
        }
    }
    return d[dist];
}

int main(){
    int n,m,src,dist;
    while(scanf("%d%d%d%d",&n,&m,&src,&dist) != EOF){
        init();
        int l = 1<<30,r = -1,ans = 1<<30;
        for(int i = 0;i < m;i++){
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            add_edge(a,b,c);
            add_edge(b,a,c);
            l = min(l,c);
            r = max(r,c);
        }
        while(l <= r){
            int mid = (l+r)>>1;
            int tmp = dijkstra(src,dist,mid);
            if(tmp == -1)    l = mid+1;
            else    r = mid-1,ans = tmp;
        }

        printf("%d
",ans);
    }
    return 0;
}

•Problem D  CSU 1290                               DP

#include <cstdio>
double dp[1005];
int main()
{
    int n,t;
    double k;
    scanf("%d", &t);
    while (t--) {
        scanf("%lf %d", &k, &n);
        dp[1] = 1.0;
        for (int i = 2; i <= n; ++i)
            dp[i] = dp[i-1] + (k - dp[i-1])/k;
        printf("%.5f
", dp[n]);
    }
    return 0;
}