Va 1149: bin packing (Greedy)

Given the weight of N items, the size of the backpack is M. A backpack can hold up to two items. Ask how many backpacks at least.

Idea: greedy, maximum, and minimum. If this is not the case, the greatest one must be lonely for life. Otherwise, the rows are accompanied.

Code:

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define N 100100int a[N];int main() {    int t;    scanf("%d", &t);    bool isfirst = true;    while (t--) {        if (isfirst) isfirst = false;        else puts("");        int n;        scanf("%d", &n);        int l;        scanf("%d", &l);        for (int i = 0; i < n; i++) {            scanf("%d", &a[i]);        }        sort(a,a+n);        int st = 0;        int ed = n-1;        int cnt = 0;        while (st <= ed) {            if (st != ed){                if (a[st]+a[ed] <= l) {                    st++;                    ed--;                    cnt++;                } else {                    ed--;                    cnt++;                }            } else {                cnt++;                ed--;            }        }        printf("%d\n", cnt);    }    return 0;}

 

Va 1149: bin packing (Greedy)