[Daily Blue Bridge] 29. One-five-year provincial competition Java group real question "addition to multiplication"

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Title: Addition to Multiplication

We all know that 1+2+3+...+49=1225

Now you are required to turn the two non-adjacent plus signs into multiplication signs so that the result is 2015

For example: 1+2+3+...+9+10*11+12+...+27*28+29+...+49=2015

Is the answer that meets the requirements

Please look for another possible answer and submit the number before the multiplication sign in the front position (for example, 10 is required)

Note: What you need to submit is an integer, do not fill in any extra content

Problem-solving ideas:

For this question, we can first enumerate the positions of the first and second plus signs, and then judge the formula based on it. If you study the formula carefully, you can actually find:

Answer source code:

public class Year2015_Bt6 {

	public static void main(String[] args) {
		
		for (int i = 1; i <= 46; i++) {
			for (int j = i+2; j <= 48; j++) {
				//因为当加号变成乘号之后，除了i、i+1和j、j+1位变化，其他位均未变化，
				//所以只需要验证i*(i+1)-(i+i+1)+j*(j+1)-(j+j+1)的差值是否等于2015-1225即可
				if (i*(i+1)-(i+i+1)+j*(j+1)-(j+j+1)==2015-1225) {
					System.out.println(i + " " + j);			
				}
			}
			
		}
	}

}

 

Sample output:

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