codeforce C. Maximal Intersection
http://codeforces.com/contest/1029/problem/C
从第一天吃晚饭做到第二天吃完饭……你无法想象我的代码曾经150行 o(￣┰￣*)ゞ
找到所有线段最远的左边和最近的右边，当一个线段的左边或右边与上述重合就尝试删除。
1 import java.util.Arrays; 2 import java.util.Scanner; 3 4 public class A { 5 public static void main(String[] args) { 6 Scanner io = new Scanner(System.in); 7 int n = io.nextInt(); 8 if (n == 1) { 9 System.out.println(-(io.nextInt() - io.nextInt())); 10 return; 11 } 12 int[] a = new int[n]; 13 int[] b = new int[n]; 14 int[] A = new int[n]; 15 int[] B = new int[n]; 16 int[] minLeft = new int[n]; 17 int[] minRight = new int[n]; 18 int[] maxLeft = new int[n]; 19 int[] maxRight = new int[n]; 20 21 for (int i = 0; i < n; i++) { 22 A[i] = a[i] = io.nextInt(); 23 B[i] = b[i] = io.nextInt(); 24 if (i != 0) { 25 maxLeft[i] = Math.max(maxLeft[i - 1], a[i]); 26 minLeft[i] = Math.min(minLeft[i - 1], b[i]); 27 } else { 28 maxLeft[0] = a[0]; 29 minLeft[0] = b[0]; 30 } 31 } 32 for (int i = n - 1; i >= 0; i--) { 33 if (i != n - 1) { 34 maxRight[i] = Math.max(maxRight[i + 1], a[i]); 35 minRight[i] = Math.min(minRight[i + 1], b[i]); 36 } else { 37 maxRight[n - 1] = a[n - 1]; 38 minRight[n - 1] = b[n - 1]; 39 } 40 } 41 Arrays.sort(A); 42 Arrays.sort(B); 43 44 int len = 0,min,max; 45 for (int i = 0; i < n; i++) { 46 if (a[i] == A[n - 1] || b[i] == B[0]) { 47 if (i == 0) { 48 min = minRight[1]; 49 max = maxRight[1]; 50 } else if (i == n - 1) { 51 min = minLeft[n - 2]; 52 max = maxLeft[n - 2]; 53 } else { 54 min = Math.min(minLeft[i - 1], minRight[i + 1]); 55 max = Math.max(maxLeft[i - 1], maxRight[i + 1]); 56 } 57 len = Math.max(min - max, len); 58 } 59 } 60 System.out.println(len); 61 } 62 }
