result += a +b in c++ meaning
result += a + b;
a + b: Adds the values of variablesaandb.result += a + b: Adds the result of step 1 to the current value of the variableresultand assigns the sum back toresult.
result += a + b;
a + b: Adds the values of variables a and b.result += a + b: Adds the result of step 1 to the current value of the variable result and assigns the sum back to result.