回溯

#include <bits/stdc++.h>
#define sc(x) scanf("%lld", &(x))
#define pr(x) printf("%lld\n", (x))
#define rep(i, l, r) for (int i = (l); i <= (r); ++i)
using namespace std;
typedef long long ll;
const int N = 105;
const int mod = 1e9 + 7;
int a[N], car[N];
int ans = 0x3f3f3f3f;
int n, w;
void dfs(int idx, int p) {
    if (p >= ans) return;
    if (idx == n + 1) {
        ans = min(p, ans);
        return;
    }
    rep(i, 1, p) if (car[i] + a[idx] <= w) {  // 可以上车
        car[i] += a[idx];
        dfs(idx + 1, p);
        car[i] -= a[idx];  // 回溯
    }
    if (idx != 1) {  // 单独放
        car[++p] = a[idx];
        dfs(idx + 1, p);
    }
}
int main() {
    scanf("%d%d", &n, &w);
    rep(i, 1, n) scanf("%d", a + i);
    dfs(1, 1);
    printf("%d", ans);
    return 0;
}