UVa 714 Copying Books——二分最大值最小化

注意上界在累加时可能超过int范围

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

int m, k;
long long a[1000];

bool judge(long long x) {
long long sum = 0, cnt = 1;
for (int i = m; i >= 1; i--) {
sum += a[i];
if (sum > x) {
sum = a[i];
cnt++;
if (cnt > k) return false;
}
}
return true;
}

void output(int ans) {
int gang[1000];
memset(gang, 0, sizeof(gang));
long long sum = 0, cnt = 1;
for (int i = m; i >= 1; i--) {
sum += a[i];
if (sum > ans) {
sum = a[i];
cnt++;
gang[i] = 1;
}
if (k - cnt == i) {
for (; i >= 1; i--) {
gang[i] = 1;
}
break;
}
}
int flag = 0;
for (int i = 1; i <= m; i++) {
if (flag++) printf(" ");
printf("%d", a[i]);
if (gang[i]) printf(" /");
}
printf("\n");
}

int main()
{
int T; scanf("%d", &T);
while (scanf("%d %d", &m, &k) == 2) {
long long L = 0, R = 0;
for (int i = 1; i <= m; i++) {
scanf("%lld", &a[i]);
R += a[i];
if (a[i] > L) L = a[i];
}
while (L <= R) {
long long x = L + (R - L) / 2;
if (judge(x)) R = x - 1;
else L = x + 1;
}
output(L);
}
return 0;
}