P1102 A-B 数对 二分

import java.util.Arrays;
import java.util.Scanner;public class Main {public static void main(String[] args) {//A-B=CScanner sc = new Scanner(System.in);int n = sc.nextInt();int C = sc.nextInt();int[] res = new int[n+1];for(int i=1;i<=n;i++) {res[i] = sc.nextInt();}Arrays.sort(res,1,n+1);//1long ans = 0;//2for(int i=1;i<=n;i++) {//枚举Bint l1 = i,r1 = n;//二分Awhile(l1<r1) {int mid = (l1+r1)/2;if(res[mid]-res[i]>=C)	r1 = mid;else	l1 = mid+1;}int l2 = i,r2 = n;while(l2<r2) {int mid = (l2+r2+1)/2;if(res[mid]-res[i]<=C)	l2 = mid;else	r2 = mid-1;}if(res[l2] - res[i] == C) {ans+=(l2-l1)+1;}}System.out.println(ans);}
}

789. 数的范围 二分

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int n = sc.nextInt();int k = sc.nextInt();int[] res = new int[n];for(int i=0;i<n;i++)res[i] = sc.nextInt();while(k--!=0) {int x = sc.nextInt();//先大于等于再小于等于int l1 = 0,r1 = n-1;while(l1<r1) {int mid1 = (l1+r1)/2;if(res[mid1]>=x) r1 = mid1;else	l1 = mid1+1;}if(res[l1] == x) {int l2 = 0,r2 = n-1;while(l2<r2) {int mid2 = (l2+r2+1)/2;if(res[mid2]<=x) l2 = mid2;else	r2 = mid2-1; }System.out.println(l1+" "+l2);}else {System.out.println("-1 -1");}}}
}