贪心算法QwQ

P2240 【深基12.例1】部分背包问题

答案

#include <bits/stdc++.h>
using namespace std;struct Node{//金币结构体int w,v;
}a[110];int read(){int x=0,f=1;char c=getchar();while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}return x*f;
}bool cmp(Node aa,Node bb){return aa.v*bb.w>aa.w*bb.v;//按性价比从高到低排序，为防止精度问题直接交叉相乘
}int main(){int n=read(),m=read();double ans=0;for(int i=1;i<=n;i++){a[i].w=read(),a[i].v=read();}sort(a+1,a+n+1,cmp);for(int i=1;i<=n;i++){if(a[i].w<=m){ans+=a[i].v;m-=a[i].w;}else{ans+=a[i].v*m*1.0/(a[i].w*1.0);//*1.0强转doublebreak;}}printf("%.2lf",ans);return 0;
}

P1223 排队接水

答案

#include <bits/stdc++.h>
using namespace std;struct Node {int n, t;
} a[1010];// 按照接水时间从小到大排序
bool cmp(Node aa, Node bb) {return aa.t < bb.t;
}// 读入函数
int read() {int x = 0, f = 1;char c = getchar();while (c < '0' || c > '9') {if (c == '-') {f = -1;}c = getchar();}while (c >= '0' && c <= '9') {x = x * 10 + c - '0';c = getchar();}return x * f;
}int main() {int N = read();double ans = 0;// 读取每个人的接水时间for (int i = 1; i <= N; i++) {a[i].t = read();a[i].n = i;}// 对接水时间从小到大排序sort(a + 1, a + N + 1, cmp);// 输出排队顺序for (int i = 1; i <= N; i++) {printf("%d ", a[i].n);if (i < N) { // 前面的所有人需要等待ans += a[i].t * (N - i);}}printf("\n");// 计算平均等待时间并输出printf("%.2lf\n", ans / N);return 0;
}

P1803 凌乱的yyy / 线段覆盖

答案

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int N;struct act{int start;int end;
}a[1000010]; bool cmp(act a,act b){return a.end<b.end;
}int greedy(){int num=1,i=0;for(int j=1;j<=N;j++){if(a[j].start>=a[i].end){i=j;num++;}}return num;
}int main(){scanf("%d",&N);for(int i=0;i<N;i++){scanf("%d%d",&a[i].start,&a[i].end);}sort(a,a+N,cmp);int ans=greedy();printf("%d\n",ans);return 0;
}