解题报告 『活动安排（贪心）』

原题地址

第一次提交WA了两个点，因此特地写一篇博客。

 

错误见代码：

#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (register int i = (a); i <= (b); i++)

const int maxn = 1e3 + 5;

int n, ans = 0;

struct node {
    int start, end;
}work[maxn];

struct cmp {
    inline bool operator()(const node &a, const node &b) {
        return a.end < b.end;
    }
};

int read() {
    int x = 0, flag = 0;
    char ch = ' ';
    while (ch != '-' && (ch < '0' || ch > '9')) ch = getchar();
    if (ch == '-') {
        flag = 1;
        ch = getchar();
    }
    while (ch >= '0' && ch <= '9') {
        x = (x << 1) + (x << 3) + ch - '0';
        ch = getchar();
    }
    return flag ? -x : x; 
}

void write(int x) {
    if (x < 0) {
        putchar('-');
        x = -x;
    }
    if (x > 9) write(x / 10);
    putchar(x % 10 + '0');
}

int main() {
    n = read();
    rep(i, 1, n) work[i].start = read(), work[i].end = read();
    sort(work + 1, work + n + 1, cmp());
    int now = -1;
    rep(i, 1, n) {
        if (work[i].start > now) {//此处应改为work[i].start >= now.条件允许的情况下,一个活动结束后可以马上开始下一个活动. 
            ans++;
            now = work[i].end;
        }
    }
    write(ans);
    return 0;
}