UVA-1595 对称轴 题解答案代码 算法竞赛入门经典第二版

​​GitHub - jzplp/aoapc-UVA-Answer: 算法竞赛入门经典 例题和习题答案 刘汝佳 第二版​​

AC代码

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

struct point {
  int x, y;
};

bool cmp1(const point &lhs, const point &rhs) {
  if(lhs.x != rhs.x) {
    return lhs.x < rhs.x;
  }
  return lhs.y < rhs.y;
} 

bool cmp2(const point &lhs, const point &rhs) {
  if(lhs.x != rhs.x) {
    return lhs.x < rhs.x;
  }
  return lhs.y > rhs.y;
} 

int main() {
  int t, n, i, j, k, a, b;
  cin >> t;
  bool cut2, flag; 
  while(t--) {
    vector<point> v;
    cin >> n;
    for(i = 0; i < n; ++i) {
      point p;
      cin >> p.x >> p.y;
      v.push_back(p);
    }
    sort(v.begin(), v.end(), cmp1);
    int beg1 = 0, end1, beg2, end2 = n - 1, xcut;
    cut2 = false;
    if(n % 2 == 0) {
      end1 = n/2 - 1;
      beg2 = n/2;
      int sum = v[beg2].x + v[end1].x;
      xcut = sum / 2;
      if(sum % 2 != 0) {
        cut2 = true;
      }
      // xcut = (v[n/2].x + v[n/2 - 1].x) / 2;
    } else {
      xcut = v[n/2].x;
      end1 = n/2 - 1;
      beg2 = n/2 + 1;
    }
    sort(v.begin() + beg2, v.end(), cmp2);
    flag = true;
    for(i = beg1; i <= end1; ++i) {
      a = i;
      b = end2 - i;
      if(v[a].x == xcut && v[b].x == xcut) {
        continue;
      }
      if(v[a].y != v[b].y) {
        flag = false;
        break;
      }
      if(!cut2) {
        if((xcut - v[a].x) != (v[b].x - xcut)) {
          flag = false;
          break;
        }
      }
      if(cut2) {
        if((xcut - v[a].x) != (v[b].x - xcut - 1)) {
          flag = false;
          break;
        }
      }
    }
    if(flag) {
      cout << "YES" << endl;
    } else {
      cout << "NO" << endl;
    }
  }
  return 0;
}