贪心算法入门

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贪心算法入门

完美字符串

    #include <iostream>    #include <cstdlib>    #include <stdio.h>    #include <algorithm>    #include <math.h>    #include <string.h>    #include <queue>    #include <stack>    typedef long long ll;    using namespace std;    int cmp(int x,int y){return x>y;}    int main(){        char s[10010];        char b[30]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};        char b1[30]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};        int  c[30],sum=0;        int zzz=26;        memset(c,0,sizeof(c));        cin>>s;        for (int i = 0; i < strlen(s); i++)        {            for (int j = 0; j <=25; j++)            {                if(s[i]==b[j]||s[i]==b1[j]){                    c[j]++;               }            }        }        sort(c,c+26,cmp);        for (int i = 0; i<=25; i++){             sum+=zzz*c[i];             zzz--;        }                printf("%d\n",sum);        return 0;    }

活动安排问题

思路以末尾排序，开个结构体对末尾时间排序，然后从第一个开始“安排”能安上的安上不能安上的拿走

    #include <iostream>    #include <cstdlib>    #include <stdio.h>    #include <algorithm>    #include <math.h>    #include <string.h>    #include <queue>    #include <stack>    #include <vector>    #include <map>    #include <set>    typedef long long ll;    using namespace std;    struct zz    {        int a;        int b;    }s[10010];    int cmp(struct zz p,struct zz q)    {        return p.b<q.b;    };    int main(){        int n;        int sum;        while(cin>>n){            sum=1;            for(int i=0;i<n;i++){                cin>>s[i].a>>s[i].b;            }            sort(s,s+n,cmp);            for(int i=0;i<n;i++){             //cout<<s[i].a<<" "<<s[i].b<<endl;             }            int text;            text =s[0].b;            for(int i=1;i<n;i++){                if(text<=s[i].a){                    sum++;                     //cout<<s[i].a<<" "<<s[i].b<<endl;                    text=s[i].b;                }            }            cout<<sum<<endl;        }        return 0;    }

独木舟问题

思路 sort一边从头尾开始往中间加

#include <iostream>#include <cstdlib>#include <stdio.h>#include <algorithm>#include <math.h>#include <string.h>#include <queue>#include <stack>#include <vector>#include <map>#include <set>typedef long long ll;using namespace std;int main(){    int n,m,sum;  //  N 人数 M 承重    int a[10000];    cin>> n >> m;    sum=0;    for(int i=0;i<n;i++){            cin>>a[i];    }    sort(a, a+n);    int p,q;    p=0;    q=n-1;    while(p<=q){        if(a[p]+a[q]<=m){sum++;q--;p++;}        else{sum++;q--;}    }    printf("%d\n",sum);    return 0;}

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