C - Tsundoku https://atcoder.jp/contests/abc172/tasks/abc172_c

abc172_c.py

N, M, K = map(int, input().split())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
sumA = [0]
for i in range(N):
    sumA.append(sumA[-1] + A[i])
sumB = [0]
for i in range(M):
    sumB.append(sumB[-1] + B[i])
ans = 0
for i in range(len(sumA)):
    # Aをi冊選んだとき、Bが何冊読めるか?
    rest = K - sumA[i]
    if rest < 0:
        continue
    ok, ng = 0, len(sumB)
    while ng - ok > 1:
        mid = (ok + ng) // 2
        if sumB[mid] <= rest:
            ok = mid
        else:
            ng = mid
    ans = max(i + ok, ans)
print(ans)