Leetcode[python]: Two Sum

twosum.py

class Solution:
    # @num list of values.
    # @return list of tuples in [(val, index)...], i.e. [2,1,3] -> [(1,1),(2,0),(3,2)].
    def sortedNumbersWithIndex(self, num):
        tuples = [];
        for i in range(len(num)):
            tup = (num[i], i);
            tuples.append(tup);
        tuples.sort(key=lambda tup: tup[0]);
        return tuples;
        
    # @return a tuple, (index1, index2)
    def twoSum(self, num, target):
        keyedNum = self.sortedNumbersWithIndex(num);
        
        a = 0;
        b = len(keyedNum)-1;
        while (a < b):
            va = keyedNum[a][0];
            vb = keyedNum[b][0];
            ia = min(keyedNum[a][1], keyedNum[b][1]);
            ib = max(keyedNum[a][1], keyedNum[b][1]);
            if (va+vb==target):
                return (ia+1,ib+1)
                
            elif (va+vb<target):
                a +=1
                
            else:
                b -=1;