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Description
The figure shown on the left is left-right symmetric as it is possible to fold the sheet of paper along a vertical line, drawn as a dashed line, and to cut the figure into two identical halves. The figure on the right is not left-right symmetric as it is impossible to find such a vertical line.
Write a program that determines whether a figure, drawn with dots, is left-right symmetric or not. The dots are all distinct.
Input
The input consists of T test cases. The number of test cases T is given in the first line of the input file. The first line of each test case contains an integer N , where N ( 1N1, 000) is the number of dots in a figure. Each of the following N lines contains the x-coordinate and y-coordinate of a dot. Both x-coordinates and y-coordinates are integers between -10,000 and 10,000, both inclusive.
Output
Print exactly one line for each test case. The line should contain `YES‘ if the figure is left-right symmetric. and `NO‘, otherwise.
The following shows sample input and output for three test cases.
Sample Input
3 5 -2 5 0 0 6 5 4 0 2 3 4 2 3 0 4 4 0 0 0 4 5 14 6 10 5 10 6 14
Sample Output
YES NO YES 分析:我的思路是输入的同时,记下某一行的x的最大值和最小值,通过这一行的对称轴,再默认已它为所有行的对称轴去判断是否适用其他行,没有冲突即找到对称轴。 我的代码
#include<iostream> #include<cstdio> #include<algorithm> #include<map> using namespace std; struct point { double x, y; point(int x1 = 0, int y1 = 0) :x(x1), y(y1) {} void mirror() { x = -x; } bool operator <(const point &b)const { if (x == b.x){ return (y< b.y); } else{ return x < b.x; } } }p[1010]; map<point, bool> m; bool findmirror(point & p1, double x) { point tempp; tempp.x = 2 * x - p1.x; tempp.y = p1.y; //auto result =m.find(tempp); if (m[tempp]){ return true; } return false; } int Max = -15000; int Min = 15000; int main() { int t; cin >> t; while (t--){ m.clear(); bool flag = true; Max = -15000; Min = 15000; int n; cin >> n; //输入 for (int i = 0; i < n; i++){ cin >> p[i].x >> p[i].y; m[p[i]] = true; if (p[i].y == p[0].y){ if (Max < p[i].x) Max = p[i].x; if (Min>p[i].x) Min = p[i].x; } } //判断 double mir = (double)(Max + Min) / 2; for (int i = 0; i < n; i++){ if ( !findmirror(p[i], mir) ){ flag = false; break; } } if (flag == true) puts("YES"); else puts("NO"); } return 0; }