221 - Urban Elevations （UVA）

题目链接如下：

Online Judge

正确的解法在这里（也是刘汝佳的思路）：UVA ~ 221 ~ Urban Elevations （离散化）-CSDN博客

我开始的代码如下（代码虽然AC了，但是是有问题的，uva的测试数据太水了所以侥幸通过而已。因为题目要求的数据是实数而非整数，我的代码是按所有数据都是整数来暴力做的……）：

#include 
#include 
#include 
#include 
// #define debug
const int maxx = 1000000;

struct building{
    int x, y, width, depth, height, number;
    building(){}
    building(int _x, int _y, int _width, int _depth, int _height): x(_x), y(_y), width(_width), depth(_depth), height(_height){}
};
int n, x, y, width, depth, height, kase = 0;
std::vector vec;
std::vector ans[maxx];

bool cmp1(const int &a, const int &b){
    return vec[a - 1].y < vec[b - 1].y;
}

bool cmp2(const int &a, const int &b){
    return vec[a - 1].x != vec[b - 1].x ? vec[a - 1].x < vec[b - 1].x : (vec[a - 1].y < vec[b - 1].y);
}

int main(){
    #ifdef debug
    freopen("1.txt", "r", stdin);
    freopen("2.txt", "w", stdout);
    #endif
    while(scanf("%d", &n) == 1 && n){
        printf("%s", kase ? "\n" : "");
        printf("For map #%d, the visible buildings are numbered as follows:\n", ++kase);
        std::vector tmp;
        fill(ans, ans + maxx, tmp);
        int maxWidth = 0;
        int minWidth = 10000000;
        vec.clear();
        for(int i = 1; i <= n; ++i){
            scanf("%d %d %d %d %d", &x, &y, &width, &depth, &height);
            vec.push_back(building(x, y, width, depth, height));
            vec.back().number = i;
            maxWidth = std::max(maxWidth, x + width);
            minWidth = std::min(minWidth, x);
            for(int j = x; j < x + width; ++j){
                ans[j].push_back(i);
            }
        }
        for(int i = minWidth; i < maxWidth; ++i){
            sort(ans[i].begin(), ans[i].end(), cmp1);
            int height = 0;
            for(int j = 0; j < ans[i].size(); ++j){
                if(vec[ans[i][j] - 1].height > height){
                    height = vec[ans[i][j] - 1].height;
                } else{
                    ans[i][j] = 0;
                }
            }
        }
        std::vector res;
        std::set st;
        for(int i = minWidth; i < maxWidth; ++i){
            for(int j = 0; j < ans[i].size(); ++j){
                if(ans[i][j] && st.find(ans[i][j]) == st.end()){
                    res.push_back(ans[i][j]);
                    st.insert(ans[i][j]);
                }
            }
        }
        sort(res.begin(), res.end(), cmp2);
        for(int i = 0; i < res.size(); ++i){
            printf("%d%s", res[i], i == res.size() - 1 ? "\n" : " ");
        }
    }
    #ifdef debug
    fclose(stdin);
    fclose(stdout);
    #endif
    return 0;
}

后来把刘汝佳的想法和我原先的想法综合了一下，改写成下面的代码：

#include 
#include 
#include 
#include 
// #define debug

struct building{
    double x, y, width, depth, height;
    building(double _x, double _y, double _width, double _depth, double _height): x(_x), y(_y), width(_width), depth(_depth), height(_height){}
};
double x, y, width, depth, height;
int n, kase = 0;
std::set pts;
std::vector vec;

bool cmp1(const int &a, const int &b){
    return vec[a].y < vec[b].y;
}

bool cmp2(const int &a, const int &b){
    return vec[a].x != vec[b].x ? vec[a].x < vec[b].x : (vec[a].y < vec[b].y);
}

int main(){
    #ifdef debug
    freopen("1.txt", "r", stdin);
    freopen("2.txt", "w", stdout);
    #endif
    while(scanf("%d", &n) == 1 && n){
        printf("%s", kase ? "\n" : "");
        printf("For map #%d, the visible buildings are numbered as follows:\n", ++kase);
        vec.clear();
        pts.clear();
        for(int i = 1; i <= n; ++i){
            scanf("%lf %lf %lf %lf %lf", &x, &y, &width, &depth, &height);
            vec.push_back(building(x, y, width, depth, height));
            pts.insert(x);
            pts.insert(x + width);
        }
        std::vector res;
        double start = *(pts.begin());
        for(auto it = ++pts.begin(); it != pts.end(); ++it){
            double h = 0.0;
            std::vector temp;
            double middle = (start + *it) / 2;
            for(int i = 0; i < vec.size(); ++i){
                if((vec[i].x < middle && vec[i].x + vec[i].width > middle)){
                    temp.push_back(i);
                }
            }
            sort(temp.begin(), temp.end(), cmp1);
            for(int i = 0; i < temp.size(); ++i){
                if(vec[temp[i]].height > h){
                    h = vec[temp[i]].height;
                    if(find(res.begin(), res.end(), temp[i]) == res.end()){
                        res.push_back(temp[i]);
                    }
                }
            }
            start = *it;
        }
        sort(res.begin(), res.end(), cmp2);
        for(int i = 0; i < res.size(); ++i){
            printf("%d%s", res[i] + 1, i == res.size() - 1 ? "\n" : " ");
        }
    }
    #ifdef debug
    fclose(stdin);
    fclose(stdout);
    #endif
    return 0;
}