D - LRUD Instructions

https://atcoder.jp/contests/abc273/tasks/abc273_d

分析

横坐标和纵坐标很大，不能采用二维数组形式，否则内存干爆，

目标对象移动，按照指令进行移动， 每次沿垂直或者水平方向，

那么这里对每一个墙， 都记录两点，即可满足判断需求：

1. 每个水平方向上的障碍
2. 每个竖直方向上的障碍

使用map<int, vector<int>>, 然后对vector<int>进行sort

最后在目标移动的使用，在vector<int>中使用upper_bound判断其位置。

Code

https://atcoder.jp/contests/abc273/submissions/35962591

int h,w;
int rs, cs;
int n, q;
map<int, vector<int>> xblocks;
map<int, vector<int>> yblocks;
 
int main()
{
    cin >> h >> w;
    cin >> rs >> cs;
    cin >> n;
    
    /*
        store x-direction blocks, i.e. ci
        store y-direction blocks, i.e. ri
    */
    for(int i=0; i<n; i++){
        int ri, ci;
        cin >> ri >> ci;
        vector<int>& tempx = xblocks[ri];
        tempx.push_back(ci);
        
        vector<int>& tempy = yblocks[ci];
        tempy.push_back(ri);
    }
 
    /*
    sort all blocks of each x-directions
    */
    map<int, vector<int>>::iterator it;
    for(it=xblocks.begin(); it!=xblocks.end(); it++){
        vector<int>& block_list = it->second;
        
        sort(block_list.begin(), block_list.end());
    }
 
    /*
    sort all blocks of each y-directions
    */
    for(it=yblocks.begin(); it!=yblocks.end(); it++){
        vector<int>& block_list = it->second;
 
        sort(block_list.begin(), block_list.end());
    }
 
    cin >> q;
    // ri ci are position where T is moving
    int ri = rs;
    int ci = cs;
    for(int i=0; i<q; i++){
        string di;
        int li;
        cin >> di >> li;
        
        // horizontal blocks
        vector<int>& hb = xblocks[ri];
 
        // vertical blocks
        vector<int>& vb = yblocks[ci];
 
        vector<int>::iterator low, up;
        
        if (di == "L"){
            // no block in that row
            if(hb.size() == 0){
//                cout << "ci = " << ci << endl;
//                cout << "li = " << li << endl;
                int pos = ci - li;
                ci = pos>0?pos:1;
                cout << ri << " " << ci << endl;
                continue;
            }
            
            int first = hb[0];
            int last = hb[hb.size()-1];
            if (ci < first){
                int pos = ci - li;
                ci = pos>0?pos:1;
                cout << ri << " " << ci << endl;
                continue;
            }
            
            if (ci > last){
                int pos = ci - li;
                ci = pos>last?pos:(last+1);
 
                cout << ri << " " << ci << endl;
                continue;
            }
            
            up = upper_bound(hb.begin(), hb.end(), ci);
            int upindex = up - hb.begin();
            int base = hb[upindex-1];
            int pos = ci - li;
            ci = pos>base?pos:(base+1);
            
            cout << ri << " " << ci << endl;
        } else if (di == "R") {
            // no block in that row
            if(hb.size() == 0){
                int pos = ci + li;
                ci = pos<=w?pos:w;
                cout << ri << " " << ci << endl;
                continue;
            }
 
            int first = hb[0];
            int last = hb[hb.size()-1];
            if (ci < first){
                int pos = ci + li;
                ci = pos<first?pos:(first-1);
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            if (ci > last){
                int pos = ci + li;
                ci = pos<=w?pos:w;
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            up = upper_bound(hb.begin(), hb.end(), ci);
            int upindex = up - hb.begin();
            int top = hb[upindex];
            int pos = ci + li;
            ci = pos<top?pos:top-1;
 
            cout << ri << " " << ci << endl;
        } else if (di == "U") {
            // no block in that column
            if(vb.size() == 0){
                int pos = ri - li;
                ri = pos>0?pos:1;
                cout << ri << " " << ci << endl;
                continue;
            }
 
            int first = vb[0];
            int last = vb[vb.size()-1];
            if (ri < first){
                int pos = ri - li;
                ri = pos>0?pos:1;
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            if (ri > last){
//                cout << "ri = " << ri << endl;
//                cout << "li = " << li << endl;
//                cout << "last = " << last << endl;
                
                int pos = ri - li;
                ri = pos>last?pos:(last+1);
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            up = upper_bound(vb.begin(), vb.end(), ri);
            int upindex = up - vb.begin();
 
            int top = vb[upindex-1];
            int pos = ri - li;
            ri = pos>top?pos:(top+1);
            
            cout << ri << " " << ci << endl;
        } else if (di == "D") {
            // no block in that column
            if(vb.size() == 0){
                int pos = ri + li;
                ri = pos<=h?pos:h;
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            int first = vb[0];
            int last = vb[vb.size()-1];
            if (ri < first){
                int pos = ri + li;
                ri = pos<first?pos:(first-1);
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            if (ri > last){
                int pos = ri + li;
                ri = pos<=h?pos:h;
 
                cout << ri << " " << ci << endl;
                continue;
            }
 
            up = upper_bound(vb.begin(), vb.end(), ri);
            int upindex = up - vb.begin();
 
            int top = vb[upindex];
            int pos = ri + li;
            ri = pos<top?pos:(top-1);
 
            cout << ri << " " << ci << endl;
        }
    }
 
    return 0;
}