POJ3273 Monthly Expense

 

　　查看原题

　　边界，就是边界和思维，怎么有效的判断中间值是大了还是小了，以及准确的找到边界！一个<写成<=就前功尽弃，还特别难找到错误！

#include <cstdio>
#include <algorithm>
const int maxN = 100005;
int N, M;
int A[maxN];
using namespace std;
int main(void) {
    while (2 == scanf("%d%d", &N, &M)) {
        int u = 0, l = 0, m, sum, cnt, i;
        for (int i = 0; i < N; i++) {
            scanf("%d", &A[i]);
            u += A[i];
            l = max(l, A[i]);
        }
        while (u > l) {
            m = (l+u)>>1;
            sum = cnt = 0;
            for (i = 0; i < N; i++) {
                sum += A[i];
                if (sum > m) {
                    cnt++;
                    sum = A[i];
                }
            }
            if (cnt < M) u = m;
            else l = m+1;
        }
        printf("%d\n", l);
    }
}