25 lines
493 B
Java
25 lines
493 B
Java
package LanQiaoOJ;
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import java.util.Scanner;
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//方法：暴力破解——时间复杂度为O(n^2)
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//范围为2e5*2e5=4e10 超时
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public class 求和2 {
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static int N=200010;
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static long[]a=new long[N];
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public static void main(String[] args) {
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Scanner sc=new Scanner(System.in);
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int n=sc.nextInt();
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for(int i=1;i<n;i++) {
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a[i]=sc.nextInt();
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}
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long ans=0;
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for(int i=1;i<=n;i++) {
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for(int j=i+1;j<=n;j++) {
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ans+=a[i]+a[j];
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}
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}
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System.out.println(ans);
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}
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}
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