99+98+97+96...+3+2+1 because the first person will call everyone but himself, then the second person only needs to call 98 people because the first person already called him (and so on). adding everything together will be 5050, and that is the number of calls to make. |
Is there a condition that every call can only transfer one message? If not, the minimum value must <= 197 step 1: person number 2~100 call person number 1 (99 calls), then person number 1 & 100 know all 100 messages. step 2: person number 1 call person number 2~99 (98 calls), then all know 100 messages. |
i don't get this. person number 2~100 call person number 1 (99 calls), then person number 1 & 100 know all 100 messages. how did person number 100 know all 100 messages? |
The key point here is that one can tell all the messages that he knows to another in one call. The topic is misleading... |
Here assume number 100 is the 99th call to number 1. When he calls, number 1 have already got message 1~99. On this call, number 100 give number 1 message number 100, number 1 give message 1~99 to number 100 |
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